title: Kelly Rowland

text: In 2010, Kelly Rowland launched I Heart My Girlfriends, a charity that focuses on self-esteem, date violence prevention, community service, abstinence, sports, drug/alcohol/smoking avoidance, obesity, disabilities, and education. In April 2010, Rowland toured Australia alongside Akon, Pitbull, Sean Paul, Jay Sean, and Eve for the Australian urban festival, Supafest. Later that month, her song "Everywhere You Go", featuring an all-star supergroup of international artists called Rhythm of Africa United, was released as the MTN theme song for the 2010 FIFA World Cup in South Africa. In October 2010, the American Society of Composers, Authors and Publishers (ASCAP) honored Rowland at the second annual ASCAP Presents Women Behind the Music, an event that recognizes women in all areas of the music industry. Rowland's first compilation album, "Work: The Best of Kelly Rowland", was released on October 25, 2010, but failed to impact the charts.


title: Kelly Rowland

text: In January 2011, Rowland reunited with Nelly on "Gone", a sequel to their successful 2002 collaboration "Dilemma". Upon its release, the song failed to reprise the success of "Dilemma". In April 2011, Rowland appeared on Italian DJ Alex Gaudino's single "What a Feeling", which became another UK top-ten hit. During this time, Rowland's boyfriend (and future husband), Tim Weatherspoon, became her manager.


title: Kelly Rowland

text: Originally scheduled for release in 2010, Rowland's third studio album "Here I Am" was released on July 26, 2011, in the United States. The album sold 77,000 copies in its first week and debuted atop the R&B/Hip-Hop Albums chart. "Here I Am" produced the successful lead single "Commander", which peaked in the top-ten of many charts in Europe, and the UK top-ten single "Down for Whatever". It also included another successful single "Motivation", with Lil Wayne, which topped the R&B/Hip-Hop Songs chart for seven consecutive weeks and was certified double platinum by the Recording Industry Association of America (RIAA). "Motivation" won Song of the Year at the 2011 Soul Train Music Awards and Top R&B Song at the 2012 Billboard Music Awards, and received a Grammy Award nomination for Best Rap/Sung Collaboration. Rowland was the face of Diddy's women's fragrance Empress, the female counterpart to his men's fragrance I Am King. She was also the worldwide ambassador for watchmakers company TW Steel. Rowland's second compilation album, "", was released on October 18, 2011, but failed to impact the charts. She also released her first fitness DVD titled "Sexy Abs with Kelly Rowland". Later that year, it was confirmed that Rowland would replace Dannii Minogue as a judge for the eighth series of "The X Factor UK" alongside Louis Walsh, Gary Barlow (who replaced Simon Cowell), and Tulisa Contostavlos (who replaced Cheryl Cole). Rowland's team of finalists in the "Girls" category, including Amelia Lily, finished in third place in one series. Rowland would also later be revealed as the judge who formed the girl group Little Mix. Due to a conflicting schedule, Rowland did not return for the ninth series in 2012 and was replaced by former judge of "The X Factor USA", Nicole Scherzinger. During the Black Women in Music event held on February 8, 2012, "Essence" magazine honored Rowland and music executive Sylvia Rhone for their contributions to music. In April 2012, Rowland toured Australia alongside Ludacris, Chris Brown, Trey Songz, T-Pain, Ice Cube, Lupe Fiasco, and Big Sean for the urban festival, Supafest. That same month, she returned to the big screen playing the supporting role of Brenda in the romantic comedy "Think Like a Man". The film, which also starred Michael Ealy, Jerry Ferrara, Meagan Good, Regina Hall, and Kevin Hart, topped the US box office and grossed $91.5 million. Rowland recorded "Need a Reason" with Future and Bei Maejor for the "Think Like a Man" soundtrack.


title: Kelly Rowland

text: In June 2012, Rowland became the face of popular rum brand Bacardi. Rowland and German production team Project B reworked the Bacardi song, "Bacardi Feeling (Summer Dreamin')", and released an accompanying music video to help promote the brand. In August 2012, Rowland became a dance master in the first season of the Australian talent show "Everybody Dance Now" alongside Jason Derulo. The show was cancelled after the fourth episode due to poor ratings.


title: Kelly Rowland

text: In January 2013, Destiny's Child released a compilation album titled "Love Songs", a collection of romance-themed songs from their previous albums, as well as the newly recorded song "Nuclear". On February 3, 2013, during Beyoncé's performance at the Super Bowl XLVII halftime show, held at the Mercedes-Benz Superdome in New Orleans, Rowland and Michelle Williams joined her on stage to perform "Bootylicious", "Independent Women" and "Single Ladies (Put a Ring on It)". On February 24, 2013, Rowland co-hosted the Academy Awards pre-show for the 85th Academy Awards alongside Kristin Chenoweth, Lara Spencer, Robin Roberts, and Jess Cagle. In May 2013, it was announced that Rowland would replace L.A. Reid as a judge on "The X Factor USA" for its third and final season, joining Simon Cowell, Demi Lovato, and fellow new judge Paulina Rubio (who was replacing Britney Spears). Rowland's finalists from the "Over 25s", including Jeff Gutt, finished as the runner-up on this final season. On "The X Factor USA", Rowland had more success and popularity as a judge than "The X Factor UK". Later that month, Rowland performed as a supporting headlining act at the RiverFest 2013 in Little Rock, Arkansas. Rowland embarked on the Lights Out Tour, a co-headlining tour with The-Dream, to promote her fourth studio album "Talk a Good Game". Formerly titled "Year of the Woman", the album was released on June 18, 2013, in the US. It is Rowland's first release with Republic Records following Universal Music Group's decision to close Universal Motown and Universal Republic and reviving Motown Records and Republic Records. "Talk a Good Game" sold 68,000 copies in its first week and debuted at number four on the "Billboard" 200, becoming Rowland's third top-ten album in the US. The album's lead single "Kisses Down Low" was a moderate success on the US R&B/Hip-Hop Songs chart and was certified gold by RIAA for exceeded 500,000 copies sold. The second and final single was "Dirty Laundry". In December 2013, Rowland appeared in Beyoncé's "Grown Woman" music video and alongside Williams in Beyoncé's "Superpower" music video and provided backing vocals on the same track, taken from her self-titled fifth studio album.


title: Kelly Rowland

text: In February 2014, Rowland was featured on Joe's single "Love & Sex Part 2". In March 2014, she was named a spokesperson for cosmetic company Caress. During an interview with "HuffPost Live" on March 26, 2014, Rowland revealed that she has begun recording her fifth studio album and said the new music, which encompasses horns, drums, and flutes, was influenced by iconic female singers including Diana Ross. Rowland also announced in the interview that she left Republic Records, adding that she "just needed a fresh, new start." In June 2014, Rowland and Beyoncé were featured on Williams' single "Say Yes". The same month, her song "The Game" and its music video appeared on Pepsi's visual album for the 2014 FIFA World Cup, titled "Beats of the Beautiful Game". On July 19, 2014, Rowland was featured on Adrian Marcel's song "Honey" from his mixtape "Weak After Next" and on Beau Vallis's song "Love Stand Still". Rowland also contributed background vocals to the song "You're My Star", the first single released from Tank's 2014 album "Stronger".


title: Kelly Rowland

text: In August 2015, she was featured on Jacob Whitesides's single "I Know What You Did Last Summer". Rowland was part of the recurring cast of the second season of the television series "Empire". She played Leah Walker, Lucious Lyon's mother, in flashbacks and starred in five episodes. She recorded a song for the show called "Mona Lisa" which was included in the EP "Empire: Music from "Be True"", released on October 21, 2015. On October 26, 2015, Rowland released a new song titled "Dumb" which is rumored to appear on her upcoming fifth album. Rowland's new record does not have a release date yet.


title: Kelly Rowland

text: Rowland, along with Missy Elliott, Kelly Clarkson, Zendaya, Janelle Monáe, Lea Michele, and Chloe x Halle were all featured on a charity single put together by US First Lady Michelle Obama. "This Is For My Girls" was written by Diane Warren and was released on March 15, 2016. The song was created to raise funds and awareness towards Obama's Let Girls Learn initiative – aimed at boosting education rates amongst adolescent girls around the world who are denied the right to an education. The iTunes-exclusive record was used to both coincide with Obama's Texan SXSW speech and to promote the "Let Girls Learn" initiative. The following month, Rowland hosted BET's documentary series "Chasing Destiny", where she and choreographer/director Frank Gatson Jr. searched to find the next superstars for an all-female group. They eventually formed the girl group June's Diary.


title: Kelly Rowland

text: On December 24, 2016, it was announced that Rowland would replace Ronan Keating as a coach on the sixth season of "The Voice Australia", which aired in early 2017. Rowland played the role of Margot Scotts in the television film "Love By the 10th Date", which premiered on Lifetime on January 28, 2017. On April 11, 2017, Kelly released her first book named "Whoa, Baby!: A Guide for New Moms Who Feel Overwhelmed and Freaked Out (and Wonder What the #*$& Just Happened)." On August 8, 2017, it was announced that Rowland was joining new judge Jennifer Hudson on the thirteenth season of The Voice US, who served as the winning coach on last season's The Voice UK. Hudson supported Rowland, a coach on the Australian version, as her advisor"." In April 2018, Rowland reunited with Beyoncé Knowles and Michelle Williams during Knowles' headlining set at the Coachella Valley Music and Arts Festival. In the seventh season of "The Voice Australia", she became the winning coach with two of her acts Sam Perry and Bella Paige became the top two, with Sam Perry as the winner and Bella Paige as the runner-up.


title: Kelly Rowland

text: In September 2018, BET announced that Rowland would star as Gladys Knight in the series "American Soul". She released a new single, "Kelly" on November 22, 2018. In February 2019, "American Soul" premiered to positive reviews. On February 6, Rowland released a second single called "Crown" with the music video in partnership with Dove for the campaign #MyHairMyCrown. In May 2019, she featured on Ciara's song "Girl Gang" from the album "Beauty Marks". On May 18, Rowland published an EP titled "The Kelly Rowland Edition" on streaming platforms. She also continued her work at The Voice Australia, starred in television series "L.A.'s Finest", Robin Thede's HBO series "A Black Lady Sketch Show", and the Christmas movie, "Merry Liddle Christmas", produced by Rowland and her husband for Lifetime in December 2019. As part of the Christmas movie, Rowland released a song, "Love You More at Christmas Time" via her own record label, KTR Records. On April 17, 2020, Rowland released a single titled "Coffee" through KTR Records. On May 6, 2020, she announced her management deal with Roc Nation. This announcement meant Rowland's husband would no longer manage her. In the ninth season of "The Voice Australia", she became the winning coach for the second time with her act Chris Sebastian as the winner.


title: Kelly Rowland

text: Rowland made a cameo in Beyoncé's Disney+ film "Black Is King" which was released globally on July 31, 2020. She appeared in the movie "Bad Hair", released on Hulu, in October 2020. Rowland recorded three songs for the movie's soundtrack. That same month, she released her second single of the year titled "Crazy" on KTR Records, along with an official lyric video. As part of the NFL's Songs of the Season campaign, Rowland released another single called "Hitman" in November 2020. An accompanying music video premiered on YouTube. Rowland continued acting, starring in "Merry Liddle Christmas Wedding", Lifetime's first-ever holiday sequel to "Merry Liddle Christmas", which aired at the end of the month. Rowland recorded a cover of "We Need a Little Christmas" to help promote the film, which she produced with her husband.


title: Kelly Rowland

text: To commemorate her fortieth birthday, Rowland released the song "Black Magic" on February 12, 2021. Her sons, Titan and Noah, make an appearance in the supporting visual. On February 19, 2021, Rowland's EP, "K", premiered on streaming platforms, alongside the music video for its opening track, "Flowers". In November 2021, Rowland released a cover of "Wonderful Time" to support her third holiday movie, "Merry Liddle Christmas Baby", which aired that month on Lifetime. In November 2022, Rowland starred alongside Marsai Martin and Omari Hardwick in the Paramount+ film "Fantasy Football".


title: Kelly Rowland

text: On December 16, 2013, Rowland announced her engagement to Tim Weatherspoon, during an appearance on "The Queen Latifah Show". They were married in Costa Rica on May 9, 2014. On June 10, 2014, Rowland announced via Instagram that she and Weatherspoon were expecting their first child. On November 4, 2014, Rowland gave birth to a son. On June 20, 2020, Rowland revealed she had reconciled with her estranged father, Christopher Lovett. On October 7, 2020, Rowland announced that she and Weatherspoon were expecting another child in the November issue of "Women's Health". On January 21, 2021, Rowland gave birth to their second son.


title: Kelly Rowland

text: Rowland's voice is classified as a three-octave lyric mezzo-soprano, and her music includes various styles of musical genres such as contemporary R&B, pop, hip hop, soul, rock, and dance. Her debut solo album "Simply Deep" (2002) followed an adult-alternative rock sound, while her second album "Ms. Kelly" (2007) featured an R&B/Hip-Hop sound. In an interview with "The Independent", Rowland admitted that with her first two albums, she struggled to find her sound. "I was in a stage with the first two records where I was searching, and I was like, let me try a rock-dance approach, the label [and management] wanted me to try it, and I did it ... And then after that came a more urban approach with "Ms. Kelly" in 2007." Her third album "Here I Am" (2011) consisted of a pop and R&B sound, with subtle influences of dance. Rowland stated that meeting David Guetta had influenced her to record dance music. During production of the album, Rowland stated that part of the reason for the new sound on "Here I Am" was wanting to do something different, saying "I knew I couldn't be afraid of this direction, and I wasn't going to let the thoughts and opinions of others make me afraid to go in this direction".


title: Kelly Rowland

text: Most of the lyrical themes in "Simply Deep" (2002) speak of love and life experiences, particularly in the songs "Dilemma", in which Rowland expresses her endless love to her love interest, and "Stole", in which she sings about an emotional "tale of school shootings and suicides". In "Ms. Kelly" (2007), Rowland covers topics such as her "deeply personal relationship issues" in her songs, "Still in Love with My Ex", "Flashback", "Love", "Better Without You" and "Gotsta Go (Part I)". Alex Macpherson of "The Guardian" noted that the songs could be about Rowland's former relationship with American football player Roy Williams. "Here I Am" (2011) included common themes of womanhood, sexual intimacy, and love. Some of Rowland's other songs such as "Work", "I'm Dat Chick" and "Work It Man" have been musically compared to the work of former Destiny's Child bandmate Beyoncé.


title: Kelly Rowland

text: Rowland has cited Whitney Houston and Janet Jackson as her biggest musical influences. She stated that Houston "was the woman that inspired me to sing." Rowland is also inspired by Sade Adu and says that "she has a style that's totally her own." Other inspirations include: Martin Luther King Jr.; Mariah Carey; Mary J. Blige; Naomi Campbell; and Oprah Winfrey, whom she describes as "the female version of God." Rowland has discussed how living in Miami has influenced her style, growth, and music. From a fashion perspective, Rowland credits Halle Berry, Jennifer Lopez, Beyoncé, Oprah, and her grandmother as her style icons. Rowland cited Whitney Houston, Beyoncé, and Brandy as vocal inspirations for her second solo album "Ms. Kelly", "I love how different they are. I love how they take themselves to the next level". Her third solo album "Here I Am" was inspired by Donna Summer and Diana Ross, as well as dance producer will.i.am. Rowland's fourth solo album "Talk a Good Game" was also inspired by Houston, Marvin Gaye, and Stevie Wonder.


title: Kelly Rowland

text: Rowland stated that there was a time in her life when she struggled with being dark-skinned. In October 2007, Rowland underwent plastic surgery to receive breast implants. She stated, "I simply went from an A-cup to a B-cup" and that "the decision was 10 years in the making". In 2012, Rowland ranked at number 61 on "Complex" magazine's list of "The 100 Hottest Female Singers of All Time" and was recognized as one of the best-dressed women by "Glamour UK". In April 2013, Rowland ranked seventh on "People"s Most Beautiful in the World list.


title: Kelly Rowland

text: Rowland branched out into acting with a guest stint on the sitcom "The Hughleys" in 2002, before appearing in other UPN shows such as "Eve" and "Girlfriends" in the years of 2003 and 2006 respectively. Having played the role of Tammy Hamilton, an ambitious 21-year-old apprentice to realtor Toni (Jill Marie Jones) in the latter sitcom, Rowland initially hoped her three-episode stint would expand to a larger recurring role, but as the show was moved to The CW network the following year plans for a return eventually went nowhere. Also, in 2003, she appeared in "American Dreams" as Martha Reeves of Martha & The Vandellas, singing a version of the group's single "Nowhere to Run".


title: Kelly Rowland

text: In 2002, Rowland was cast for her big-screen debut in the slasher film "Freddy vs. Jason", a crossover film directed by Ronny Yu. Cast as one of the female leads, she portrayed Kia Waterson, the frank best friend of lead character Lori Campbell, played by Monica Keena. Released to generally mixed reviews from critics, "Freddy vs. Jason" topped the U.S. box office, gaining $36.4 million on its first weekend. Budgeted at $25 million, "Freddy vs. Jason" was released in theatres on August 15, 2003, and became a financial success, resulting in a worldwide box office total of $114.3 million.


title: Kelly Rowland

text: The following year, Rowland returned to the big screen, this time for a lead role in the romantic comedy "The Seat Filler", starring opposite Duane Martin and Shemar Moore. Executive produced by Will Smith and Jada Pinkett Smith, the film hit theaters in the summer of 2005 and debuted at number eighteen at the box office top twenty. It eventually earned a total domestic gross ticket sales of $10.2 million. In the film, for which she recorded two songs, Rowland played a pop star who falls for an awards-show seat filler in which she mistakes for a high-profile entertainment attorney. Released to a limited number of festivals only, "The Seat Filler" went straight to DVD in 2006.


title: Kelly Rowland

text: In October 2007, Rowland auditioned for the role of Louise, Carrie Bradshaw's assistant, in the 2008 of HBO's comedy series "Sex and the City". The part eventually went to Jennifer Hudson. In fall 2007, Rowland appeared as a choirmaster on the NBC reality show "Clash of the Choirs". Rowland was among superstars like Michael Bolton, Patti LaBelle, Nick Lachey, and Blake Shelton. Rowland's choir finished fifth in the competition. In 2009, she was cast to host Bravo's reality competition series "The Fashion Show" alongside Isaac Mizrahi. The series premiered on May 7, 2009.


title: Kelly Rowland

text: On May 30, 2011, Rowland was confirmed as a judge for the eighth series of the British television show "The X Factor" to replace Dannii Minogue. In addition to her judging stint, Rowland also had a supporting role in the motion picture "Think Like a Man" (2012), which also starred Keri Hilson, Chris Brown and Gabrielle Union. On April 30, 2012, it was officially announced that Rowland had departed "The X Factor UK", due to a conflicting schedule. She was replaced by former judge of The X Factor USA, Nicole Scherzinger. Rowland was awarded Ultimate TV Personality at the 2011 Cosmopolitan Ultimate Women of the Year Awards, and TV Personality of the Year at the 2012 Glamour Women of the Years Awards, for her role on the show. In August 2012, Rowland became a dance master alongside Jason Derülo, for the first season of the Australian dance talent show "Everybody Dance Now". However, on August 21, 2012, the show was cancelled due to poor ratings.


title: Kelly Rowland

text: Rowland and the Knowles family founded the Survivor Foundation, a charitable entity set up to provide transitional housing for 2005 Hurricane Katrina victims and storm evacuees in the Houston, Texas area. The Survivor Foundation extended the philanthropic mission of the Knowles-Rowland Center for Youth, a multi-purpose community outreach facility in downtown Houston. Also, in 2005, Rowland and Knowles lent their voices to a collaboration with Kitten K. Sera, entitled "All That I'm Lookin for". The song appeared on "The Katrina CD" album, whose proceeds went to the "Recording Artists for Hope" organization.


title: Kelly Rowland

text: In 2006, Rowland joined other artists such as Pink and Avril Lavigne in ads for so-called empowerment tags for the ALDO Fights AIDS campaign, which went on sale exclusively at ALDO stores and benefited the YouthAIDS initiative. In 2007, Rowland, along with stars such as Jessica Simpson and the cast of "Grey's Anatomy" autographed pink Goody Ouchless brushes that were made available for auction on eBay, with all proceeds going to Breast Cancer Awareness. Also, the singer teamed up with Kanye West, Nelly Furtado, and Snoop Dogg to design a Nike sneaker for another eBay auction. All proceeds went to AIDS Awareness.


title: Kelly Rowland

text: In 2008, Rowland officially became an ambassador for MTV's Staying Alive Foundation, which aims to reduce discrimination against people with HIV and AIDS. She has since visited projects in Tanzania and Kenya to promote the charity, and underwent a HIV and AIDS test in Africa to raise awareness of the deadly diseases. In March 2009, she spearheaded a bone marrow drive. As reported, Rowland also is readying a new charity called I Heart My Girlfriends, which will serve as an interactive support system for teenage girls.


title: Kelly Rowland

text: In 2009, Rowland connected with Serve.MTV.com, MTV's platform to connect young people with local volunteerism opportunities, for a series of on-air PSAs. From battling homelessness to beautifying impoverished neighborhoods to saving whales, Rowland was joined by the likes of Cameron Diaz, will.i.am, and Sean Kingston as they discuss causes they volunteer to support and urge young people to join with their friends in making civil service a part of their lifestyle. Also, in 2009, Rowland, along with fellow singers Alesha Dixon and Pixie Lott, created T-shirts for River Island in aid of The Prince's Trust, profits from which help change young lives. In March 2010, Rowland launched her brand new charity, I Heart My Girlfriends. According to Rowland's official website, the charity focuses on self-esteem, date violence prevention, community service, abstinence, sports, drug and alcohol and smoking avoidance, obesity, disabilities, education, and more. On April 26, 2010, she was at Grand Ballroom's "City of Hope – Spirit of Life Awards" for a charity event.


title: Kelly Rowland

text: As a solo artist, Rowland has sold more than 40 million records worldwide. She has attained number-one singles on several charts in the United States, including one on the Billboard Hot 100 chart, two on the Hot R&B/Hip-Hop Songs chart, and three on the Hot Dance Club Songs chart. Internationally, she has achieved nine top-ten singles in the United Kingdom, including two number-ones and one UK R&B number-one, and in Australia, she has released six top-twenty singles. With her works, she has earned over 47 international sales certifications to date. Rowland has won 19 awards from 54 nominations and a star on Hollywood Walk of Fame as a Destiny's Child member. She has won four Grammy Awards from 17 nominations and has been honored by the American Society of Composers, Authors and Publishers and "Essence magazine for her contributions to music.


title: Kelly Rowland

text: In 2003, Rowland received eight nominations and won five for the single "Dilemma" (a duet with American rapper Nelly) for international awards. With "Dilemma", Rowland became the first Destiny's Child member to achieve a Billboard Hot 100 and a worldwide number-one single, and to win a Grammy Award as a solo artist. "Dilemma" was ranked fifth on The 40 Biggest Duets Of All Time of Billboard, and has been a merengue version of the song in Spanish done by Papi Sanchez, under the title "Dilema". The song was the 22nd best-selling single of the 2000 decade in the UK


title: Kelly Rowland

text: and appeared on the game "Karaoke Revolution Presents: American Idol". Beyoncé, during the promotion of Rowland's second album" Ms. Kelly", declared herself to be proud of Rowland's international successes. Rowland's second worldwide hit "When Love Takes Over" (with French DJ David Guetta) received ten international nominations and won two awards. The single's Electro Extended Mix won a Grammy Awards in "Best Non-Classical, Remixed Recording" category. Other Rowland songs that have been nominated or awarded are "Commander" and "Motivation".


title: Kelly Rowland

text: "Entertainment Weekly" named "Commander" the number-one summer jam of 2010 and it was named by "Fitness Magazine" as one of "The Top 100 Workout Songs of 2010". About "Motivation" and the frequent comparison with Beyoncé, American rapper 50 Cent named Rowland as "The Most Underrated Female" declaring "There wasn't no dance moves Beyoncé was doin' that Kelly wasn't doin'." Former Destiny's Child member LeToya Luckett speaking about Kelly Rowland and her seven-week non-consecutive R&B number one "Motivation" declared "[Kelly] is still my motivation..You know she is one of the most talented girls on the torch of this earth."


title: Kelly Rowland

text: Rowland was awarded Ultimate TV Personality at the 2011 Cosmopolitan Ultimate Women of the Year Awards, and TV Personality of the Year at the 2012 Glamour Women of the Year Awards. In 2012, Rowland was named one of Glamour's Best Dressed Women in entertainment. In 2020, Rowland was awarded an NAACP Image Award for her guest performance in the television series "American Soul" as Gladys Knight.


title: Evolution

text: Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation tends to exist within any given population as a result of genetic mutation and recombination. Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on this variation, resulting in certain characteristics becoming more common or more rare within a population. The evolutionary pressures that determine whether a characteristic is common or rare within a population constantly change, resulting in a change in heritable characteristics arising over successive generations. It is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms, and molecules.


title: Evolution

text: The theory of evolution by natural selection was conceived independently by Charles Darwin and Alfred Russel Wallace in the mid-19th century and was set out in detail in Darwin's book "On the Origin of Species". Evolution by natural selection is established by observable facts about living organisms: (1) more offspring are often produced than can possibly survive (2) traits vary among individuals with respect to their morphology, physiology, and behaviour (phenotypic variation); (3) different traits confer different rates of survival and reproduction (differential fitness); and (4) traits can be passed from generation to generation (heritability of fitness). In successive generations, members of a population are therefore more likely to be replaced by the offspring of parents with favourable characteristics. In the early 20th century, other competing ideas of evolution such as mutationism and orthogenesis were refuted as the modern synthesis concluded Darwinian evolution acts on Mendelian genetic variation.


title: Evolution

text: All life on Earth shares a last universal common ancestor (LUCA), which lived approximately 3.5–3.8 billion years ago. The fossil record includes a progression from early biogenic graphite to microbial mat fossils to fossilised multicellular organisms. Existing patterns of biodiversity have been shaped by repeated formations of new species (speciation), changes within species (anagenesis), and loss of species (extinction) throughout the evolutionary history of life on Earth. Morphological and biochemical traits are more similar among species that share a more recent common ancestor, and these traits can be used to reconstruct phylogenetic trees.


title: Evolution

text: Evolutionary biologists have continued to study various aspects of evolution by forming and testing hypotheses as well as constructing theories based on evidence from the field or laboratory and on data generated by the methods of mathematical and theoretical biology. Their discoveries have influenced not just the development of biology but numerous other scientific and industrial fields, including agriculture, medicine, and computer science.


title: Evolution

text: Evolution in organisms occurs through changes in heritable traits—the inherited characteristics of an organism. In humans, for example, eye colour is an inherited characteristic and an individual might inherit the "brown-eye trait" from one of their parents. Inherited traits are controlled by genes and the complete set of genes within an organism's genome (genetic material) is called its genotype.


title: Evolution

text: The complete set of observable traits that make up the structure and behaviour of an organism is called its phenotype. These traits come from the interaction of its genotype with the environment. As a result, many aspects of an organism's phenotype are not inherited. For example, suntanned skin comes from the interaction between a person's genotype and sunlight; thus, suntans are not passed on to people's children. However, some people tan more easily than others, due to differences in genotypic variation; a striking example are people with the inherited trait of albinism, who do not tan at all and are very sensitive to sunburn.


title: Evolution

text: Heritable traits are passed from one generation to the next via DNA, a molecule that encodes genetic information. DNA is a long biopolymer composed of four types of bases. The sequence of bases along a particular DNA molecule specifies the genetic information, in a manner similar to a sequence of letters spelling out a sentence. Before a cell divides, the DNA is copied, so that each of the resulting two cells will inherit the DNA sequence. Portions of a DNA molecule that specify a single functional unit are called genes; different genes have different sequences of bases. Within cells, the long strands of DNA form condensed structures called chromosomes. The specific location of a DNA sequence within a chromosome is known as a locus. If the DNA sequence at a locus varies between individuals, the different forms of this sequence are called alleles. DNA sequences can change through mutations, producing new alleles. If a mutation occurs within a gene, the new allele may affect the trait that the gene controls, altering the phenotype of the organism. However, while this simple correspondence between an allele and a trait works in some cases, most traits are more complex and are controlled by quantitative trait loci (multiple interacting genes).


title: Evolution

text: Some heritable changes cannot be explained by changes to the sequence of nucleotides in the DNA. These phenomena are classed as epigenetic inheritance systems. DNA methylation marking chromatin, self-sustaining metabolic loops, gene silencing by RNA interference and the three-dimensional conformation of proteins (such as prions) are areas where epigenetic inheritance systems have been discovered at the organismic level. Developmental biologists suggest that complex interactions in genetic networks and communication among cells can lead to heritable variations that may underlay some of the mechanics in developmental plasticity and canalisation. Heritability may also occur at even larger scales. For example, ecological inheritance through the process of niche construction is defined by the regular and repeated activities of organisms in their environment. This generates a legacy of effects that modify and feed back into the selection regime of subsequent generations. Descendants inherit genes plus environmental characteristics generated by the ecological actions of ancestors. Other examples of heritability in evolution that are not under the direct control of genes include the inheritance of cultural traits and symbiogenesis.


title: Evolution

text: Evolution can occur if there is genetic variation within a population. Variation comes from mutations in the genome, reshuffling of genes through sexual reproduction and migration between populations (gene flow). Despite the constant introduction of new variation through mutation and gene flow, most of the genome of a species is identical in all individuals of that species. However, even relatively small differences in genotype can lead to dramatic differences in phenotype: for example, chimpanzees and humans differ in only about 5% of their genomes.


title: Evolution

text: An individual organism's phenotype results from both its genotype and the influence of the environment it has lived in. A substantial part of the phenotypic variation in a population is caused by genotypic variation. The modern evolutionary synthesis defines evolution as the change over time in this genetic variation. The frequency of one particular allele will become more or less prevalent relative to other forms of that gene. Variation disappears when a new allele reaches the point of fixation—when it either disappears from the population or replaces the ancestral allele entirely.


title: Evolution

text: Before the discovery of Mendelian genetics, one common hypothesis was blending inheritance. But with blending inheritance, genetic variation would be rapidly lost, making evolution by natural selection implausible. The Hardy–Weinberg principle provides the solution to how variation is maintained in a population with Mendelian inheritance. The frequencies of alleles (variations in a gene) will remain constant in the absence of selection, mutation, migration and genetic drift.


title: Evolution

text: Mutations are changes in the DNA sequence of a cell's genome and are the ultimate source of genetic variation in all organisms. When mutations occur, they may alter the product of a gene, or prevent the gene from functioning, or have no effect. Based on studies in the fly "Drosophila melanogaster", it has been suggested that if a mutation changes a protein produced by a gene, this will probably be harmful, with about 70% of these mutations having damaging effects, and the remainder being either neutral or weakly beneficial.


title: Evolution

text: Mutations can involve large sections of a chromosome becoming duplicated (usually by genetic recombination), which can introduce extra copies of a gene into a genome. Extra copies of genes are a major source of the raw material needed for new genes to evolve. This is important because most new genes evolve within gene families from pre-existing genes that share common ancestors. For example, the human eye uses four genes to make structures that sense light: three for colour vision and one for night vision; all four are descended from a single ancestral gene.


title: Evolution

text: New genes can be generated from an ancestral gene when a duplicate copy mutates and acquires a new function. This process is easier once a gene has been duplicated because it increases the redundancy of the system; one gene in the pair can acquire a new function while the other copy continues to perform its original function. Other types of mutations can even generate entirely new genes from previously noncoding DNA, a phenomenon termed de novo gene birth.


title: Evolution

text: The generation of new genes can also involve small parts of several genes being duplicated, with these fragments then recombining to form new combinations with new functions (exon shuffling). When new genes are assembled from shuffling pre-existing parts, domains act as modules with simple independent functions, which can be mixed together to produce new combinations with new and complex functions. For example, polyketide synthases are large enzymes that make antibiotics; they contain up to one hundred independent domains that each catalyse one step in the overall process, like a step in an assembly line.


title: Evolution

text: One example of mutation is wild boar piglets. They are camouflage colored and show a characteristic pattern of dark and light longitudinal stripes. However, mutations in "melanocortin 1 receptor" ("MC1R") disrupt the pattern. The majority of pig breeds carry "MC1R" mutations disrupting wild-type color and different mutations causing dominant black color of the pigs.


title: Evolution

text: In asexual organisms, genes are inherited together, or "linked", as they cannot mix with genes of other organisms during reproduction. In contrast, the offspring of sexual organisms contain random mixtures of their parents' chromosomes that are produced through independent assortment. In a related process called homologous recombination, sexual organisms exchange DNA between two matching chromosomes. Recombination and reassortment do not alter allele frequencies, but instead change which alleles are associated with each other, producing offspring with new combinations of alleles. Sex usually increases genetic variation and may increase the rate of evolution.


title: Evolution

text: The two-fold cost of sex was first described by John Maynard Smith. The first cost is that in sexually dimorphic species only one of the two sexes can bear young. This cost does not apply to hermaphroditic species, like most plants and many invertebrates. The second cost is that any individual who reproduces sexually can only pass on 50% of its genes to any individual offspring, with even less passed on as each new generation passes. Yet sexual reproduction is the more common means of reproduction among eukaryotes and multicellular organisms. The Red Queen hypothesis has been used to explain the significance of sexual reproduction as a means to enable continual evolution and adaptation in response to coevolution with other species in an ever-changing environment. Another hypothesis is that sexual reproduction is primarily an adaptation for promoting accurate recombinational repair of damage in germline DNA, and that increased diversity is a byproduct of this process that may sometimes be adaptively beneficial.


title: Evolution

text: Gene flow is the exchange of genes between populations and between species. It can therefore be a source of variation that is new to a population or to a species. Gene flow can be caused by the movement of individuals between separate populations of organisms, as might be caused by the movement of mice between inland and coastal populations, or the movement of pollen between heavy-metal-tolerant and heavy-metal-sensitive populations of grasses.


title: Evolution

text: Gene transfer between species includes the formation of hybrid organisms and horizontal gene transfer. Horizontal gene transfer is the transfer of genetic material from one organism to another organism that is not its offspring; this is most common among bacteria. In medicine, this contributes to the spread of antibiotic resistance, as when one bacteria acquires resistance genes it can rapidly transfer them to other species. Horizontal transfer of genes from bacteria to eukaryotes such as the yeast "Saccharomyces cerevisiae" and the adzuki bean weevil "Callosobruchus chinensis" has occurred. An example of larger-scale transfers are the eukaryotic bdelloid rotifers, which have received a range of genes from bacteria, fungi and plants. Viruses can also carry DNA between organisms, allowing transfer of genes even across biological domains.


title: Evolution

text: Large-scale gene transfer has also occurred between the ancestors of eukaryotic cells and bacteria, during the acquisition of chloroplasts and mitochondria. It is possible that eukaryotes themselves originated from horizontal gene transfers between bacteria and archaea.


title: Evolution

text: From a neo-Darwinian perspective, evolution occurs when there are changes in the frequencies of alleles within a population of interbreeding organisms, for example, the allele for black colour in a population of moths becoming more common. Mechanisms that can lead to changes in allele frequencies include natural selection, genetic drift, gene flow and mutation bias.


title: Evolution

text: Evolution by natural selection is the process by which traits that enhance survival and reproduction become more common in successive generations of a population. It embodies three principles:


title: Evolution

text: More offspring are produced than can possibly survive, and these conditions produce competition between organisms for survival and reproduction. Consequently, organisms with traits that give them an advantage over their competitors are more likely to pass on their traits to the next generation than those with traits that do not confer an advantage. This teleonomy is the quality whereby the process of natural selection creates and preserves traits that are seemingly fitted for the functional roles they perform. Consequences of selection include nonrandom mating and genetic hitchhiking.


title: Evolution

text: The central concept of natural selection is the evolutionary fitness of an organism. Fitness is measured by an organism's ability to survive and reproduce, which determines the size of its genetic contribution to the next generation. However, fitness is not the same as the total number of offspring: instead fitness is indicated by the proportion of subsequent generations that carry an organism's genes. For example, if an organism could survive well and reproduce rapidly, but its offspring were all too small and weak to survive, this organism would make little genetic contribution to future generations and would thus have low fitness.


title: Evolution

text: If an allele increases fitness more than the other alleles of that gene, then with each generation this allele will become more common within the population. These traits are said to be "selected "for"." Examples of traits that can increase fitness are enhanced survival and increased fecundity. Conversely, the lower fitness caused by having a less beneficial or deleterious allele results in this allele becoming rarer—they are "selected "against"." Importantly, the fitness of an allele is not a fixed characteristic; if the environment changes, previously neutral or harmful traits may become beneficial and previously beneficial traits become harmful. However, even if the direction of selection does reverse in this way, traits that were lost in the past may not re-evolve in an identical form (see Dollo's law). However, a re-activation of dormant genes, as long as they have not been eliminated from the genome and were only suppressed perhaps for hundreds of generations, can lead to the re-occurrence of traits thought to be lost like hindlegs in dolphins, teeth in chickens, wings in wingless stick insects, tails and additional nipples in humans etc. "Throwbacks" such as these are known as atavisms.


title: Evolution

text: Natural selection within a population for a trait that can vary across a range of values, such as height, can be categorised into three different types. The first is directional selection, which is a shift in the average value of a trait over time—for example, organisms slowly getting taller. Secondly, disruptive selection is selection for extreme trait values and often results in two different values becoming most common, with selection against the average value. This would be when either short or tall organisms had an advantage, but not those of medium height. Finally, in stabilising selection there is selection against extreme trait values on both ends, which causes a decrease in variance around the average value and less diversity. This would, for example, cause organisms to eventually have a similar height.


title: Evolution

text: Natural selection most generally makes nature the measure against which individuals and individual traits, are more or less likely to survive. "Nature" in this sense refers to an ecosystem, that is, a system in which organisms interact with every other element, physical as well as biological, in their local environment. Eugene Odum, a founder of ecology, defined an ecosystem as: "Any unit that includes all of the organisms...in a given area interacting with the physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity, and material cycles (i.e., exchange of materials between living and nonliving parts) within the system..." Each population within an ecosystem occupies a distinct niche, or position, with distinct relationships to other parts of the system. These relationships involve the life history of the organism, its position in the food chain and its geographic range. This broad understanding of nature enables scientists to delineate specific forces which, together, comprise natural selection.


title: Evolution

text: Natural selection can act at different levels of organisation, such as genes, cells, individual organisms, groups of organisms and species. Selection can act at multiple levels simultaneously. An example of selection occurring below the level of the individual organism are genes called transposons, which can replicate and spread throughout a genome. Selection at a level above the individual, such as group selection, may allow the evolution of cooperation.


title: Evolution

text: Recombination allows alleles on the same strand of DNA to become separated. However, the rate of recombination is low (approximately two events per chromosome per generation). As a result, genes close together on a chromosome may not always be shuffled away from each other and genes that are close together tend to be inherited together, a phenomenon known as linkage. This tendency is measured by finding how often two alleles occur together on a single chromosome compared to expectations, which is called their linkage disequilibrium. A set of alleles that is usually inherited in a group is called a haplotype. This can be important when one allele in a particular haplotype is strongly beneficial: natural selection can drive a selective sweep that will also cause the other alleles in the haplotype to become more common in the population; this effect is called genetic hitchhiking or genetic draft. Genetic draft caused by the fact that some neutral genes are genetically linked to others that are under selection can be partially captured by an appropriate effective population size.


title: Evolution

text: A special case of natural selection is sexual selection, which is selection for any trait that increases mating success by increasing the attractiveness of an organism to potential mates. Traits that evolved through sexual selection are particularly prominent among males of several animal species. Although sexually favoured, traits such as cumbersome antlers, mating calls, large body size and bright colours often attract predation, which compromises the survival of individual males. This survival disadvantage is balanced by higher reproductive success in males that show these hard-to-fake, sexually selected traits.


title: Evolution

text: Genetic drift is the random fluctuation of allele frequencies within a population from one generation to the next. When selective forces are absent or relatively weak, allele frequencies are equally likely to "drift" upward or downward in each successive generation because the alleles are subject to sampling error. This drift halts when an allele eventually becomes fixed, either by disappearing from the population or by replacing the other alleles entirely. Genetic drift may therefore eliminate some alleles from a population due to chance alone. Even in the absence of selective forces, genetic drift can cause two separate populations that begin with the same genetic structure to drift apart into two divergent populations with different sets of alleles.


title: Evolution

text: According to the now largely abandoned neutral theory of molecular evolution most evolutionary changes are the result of the fixation of neutral mutations by genetic drift. In this model, most genetic changes in a population are thus the result of constant mutation pressure and genetic drift. This form of the neutral theory is now largely abandoned since it does not seem to fit the genetic variation seen in nature. A better-supported version of this model is the nearly neutral theory, according to which a mutation that would be effectively neutral in a small population is not necessarily neutral in a large population. Other theories propose that genetic drift is dwarfed by other stochastic forces in evolution, such as genetic hitchhiking, also known as genetic draft. Another concept is constructive neutral evolution (CNE), which explains that complex systems can emerge and spread into a population through neutral transitions due to the principles of excess capacity, presuppression, and ratcheting, and it has been applied in areas ranging from the origins of the spliceosome to the complex interdependence of microbial communities.


title: Evolution

text: The time it takes a neutral allele to become fixed by genetic drift depends on population size; fixation is more rapid in smaller populations. The number of individuals in a population is not critical, but instead a measure known as the effective population size. The effective population is usually smaller than the total population since it takes into account factors such as the level of inbreeding and the stage of the lifecycle in which the population is the smallest. The effective population size may not be the same for every gene in the same population.


title: Evolution

text: It is usually difficult to measure the relative importance of selection and neutral processes, including drift. The comparative importance of adaptive and non-adaptive forces in driving evolutionary change is an area of current research.


title: Evolution

text: Gene flow involves the exchange of genes between populations and between species. The presence or absence of gene flow fundamentally changes the course of evolution. Due to the complexity of organisms, any two completely isolated populations will eventually evolve genetic incompatibilities through neutral processes, as in the Bateson-Dobzhansky-Muller model, even if both populations remain essentially identical in terms of their adaptation to the environment.


title: Evolution

text: If genetic differentiation between populations develops, gene flow between populations can introduce traits or alleles which are disadvantageous in the local population and this may lead to organisms within these populations evolving mechanisms that prevent mating with genetically distant populations, eventually resulting in the appearance of new species. Thus, exchange of genetic information between individuals is fundamentally important for the development of the "Biological Species Concept".


title: Evolution

text: During the development of the modern synthesis, Sewall Wright developed his shifting balance theory, which regarded gene flow between partially isolated populations as an important aspect of adaptive evolution. However, recently there has been substantial criticism of the importance of the shifting balance theory.


title: Evolution

text: Mutation bias is usually conceived as a difference in expected rates for two different kinds of mutation, e.g., transition-transversion bias, GC-AT bias, deletion-insertion bias. This is related to the idea of developmental bias. Haldane and Fisher argued that, because mutation is a weak pressure easily overcome by selection, tendencies of mutation would be ineffectual except under conditions of neutral evolution or extraordinarily high mutation rates. This opposing-pressures argument was long used to dismiss the possibility of internal tendencies in evolution, until the molecular era prompted renewed interest in neutral evolution.


title: Evolution

text: Noboru Sueoka and Ernst Freese proposed that systematic biases in mutation might be responsible for systematic differences in genomic GC composition between species. The identification of a GC-biased "E. coli" mutator strain in 1967, along with the proposal of the neutral theory, established the plausibility of mutational explanations for molecular patterns, which are now common in the molecular evolution literature.


title: Evolution

text: For instance, mutation biases are frequently invoked in models of codon usage. Such models also include effects of selection, following the mutation-selection-drift model, which allows both for mutation biases and differential selection based on effects on translation. Hypotheses of mutation bias have played an important role in the development of thinking about the evolution of genome composition, including isochores. Different insertion vs. deletion biases in different taxa can lead to the evolution of different genome sizes. The hypothesis of Lynch regarding genome size relies on mutational biases toward increase or decrease in genome size.


title: Evolution

text: However, mutational hypotheses for the evolution of composition suffered a reduction in scope when it was discovered that (1) GC-biased gene conversion makes an important contribution to composition in diploid organisms such as mammals and (2) bacterial genomes frequently have AT-biased mutation.


title: Evolution

text: Contemporary thinking about the role of mutation biases reflects a different theory from that of Haldane and Fisher. More recent work showed that the original "pressures" theory assumes that evolution is based on standing variation: when evolution depends on the introduction of new alleles, mutational and developmental biases in the introduction can impose biases on evolution "without requiring neutral evolution or high mutation rates".


title: Evolution

text: Several studies report that the mutations implicated in adaptation reflect common mutation biases though others dispute this interpretation.


title: Evolution

text: Artificial selection is the intentional selection of traits in a population of organisms. This has been used for thousands of years in the domestication of plants and animals. More recently, such selection has become a vital part of genetic engineering, with selectable markers such as antibiotic resistance genes being used to manipulate DNA. Proteins with valuable properties have evolved by repeated rounds of mutation and selection (for example modified enzymes and new antibodies) in a process called directed evolution.


title: Evolution

text: Understanding the changes that have occurred during an organism's evolution can reveal the genes needed to construct parts of the body, genes which may be involved in human genetic disorders. For example, the Mexican tetra is an albino cavefish that lost its eyesight during evolution. Breeding together different populations of this blind fish produced some offspring with functional eyes, since different mutations had occurred in the isolated populations that had evolved in different caves. This helped identify genes required for vision and pigmentation.


title: Evolution

text: Evolutionary theory has many applications in medicine. Many human diseases are not static phenomena, but capable of evolution. Viruses, bacteria, fungi and cancers evolve to be resistant to host immune defences, as well as to pharmaceutical drugs. These same problems occur in agriculture with pesticide and herbicide resistance. It is possible that we are facing the end of the effective life of most of available antibiotics and predicting the evolution and evolvability of our pathogens and devising strategies to slow or circumvent it is requiring deeper knowledge of the complex forces driving evolution at the molecular level.


title: Evolution

text: In computer science, simulations of evolution using evolutionary algorithms and artificial life started in the 1960s and were extended with simulation of artificial selection. Artificial evolution became a widely recognised optimisation method as a result of the work of Ingo Rechenberg in the 1960s. He used evolution strategies to solve complex engineering problems. Genetic algorithms in particular became popular through the writing of John Henry Holland. Practical applications also include automatic evolution of computer programmes. Evolutionary algorithms are now used to solve multi-dimensional problems more efficiently than software produced by human designers and also to optimise the design of systems.


title: Evolution

text: Evolution influences every aspect of the form and behaviour of organisms. Most prominent are the specific behavioural and physical adaptations that are the outcome of natural selection. These adaptations increase fitness by aiding activities such as finding food, avoiding predators or attracting mates. Organisms can also respond to selection by cooperating with each other, usually by aiding their relatives or engaging in mutually beneficial symbiosis. In the longer term, evolution produces new species through splitting ancestral populations of organisms into new groups that cannot or will not interbreed. These outcomes of evolution are distinguished based on time scale as macroevolution versus microevolution. Macroevolution refers to evolution that occurs at or above the level of species, in particular speciation and extinction; whereas microevolution refers to smaller evolutionary changes within a species or population, in particular shifts in allele frequency and adaptation. Macroevolution the outcome of long periods of microevolution. Thus, the distinction between micro- and macroevolution is not a fundamental one—the difference is simply the time involved. However, in macroevolution, the traits of the entire species may be important. For instance, a large amount of variation among individuals allows a species to rapidly adapt to new habitats, lessening the chance of it going extinct, while a wide geographic range increases the chance of speciation, by making it more likely that part of the population will become isolated. In this sense, microevolution and macroevolution might involve selection at different levels—with microevolution acting on genes and organisms, versus macroevolutionary processes such as species selection acting on entire species and affecting their rates of speciation and extinction.


title: Evolution

text: A common misconception is that evolution has goals, long-term plans, or an innate tendency for "progress", as expressed in beliefs such as orthogenesis and evolutionism; realistically however, evolution has no long-term goal and does not necessarily produce greater complexity. Although complex species have evolved, they occur as a side effect of the overall number of organisms increasing and simple forms of life still remain more common in the biosphere. For example, the overwhelming majority of species are microscopic prokaryotes, which form about half the world's biomass despite their small size, and constitute the vast majority of Earth's biodiversity. Simple organisms have therefore been the dominant form of life on Earth throughout its history and continue to be the main form of life up to the present day, with complex life only appearing more diverse because it is more noticeable. Indeed, the evolution of microorganisms is particularly important to evolutionary research, since their rapid reproduction allows the study of experimental evolution and the observation of evolution and adaptation in real time.


title: Evolution

text: Adaptation is the process that makes organisms better suited to their habitat. Also, the term adaptation may refer to a trait that is important for an organism's survival. For example, the adaptation of horses' teeth to the grinding of grass. By using the term "adaptation" for the evolutionary process and "adaptive trait" for the product (the bodily part or function), the two senses of the word may be distinguished. Adaptations are produced by natural selection. The following definitions are due to Theodosius Dobzhansky:


title: Evolution

text: Adaptation may cause either the gain of a new feature, or the loss of an ancestral feature. An example that shows both types of change is bacterial adaptation to antibiotic selection, with genetic changes causing antibiotic resistance by both modifying the target of the drug, or increasing the activity of transporters that pump the drug out of the cell. Other striking examples are the bacteria "Escherichia coli" evolving the ability to use citric acid as a nutrient in a long-term laboratory experiment, "Flavobacterium" evolving a novel enzyme that allows these bacteria to grow on the by-products of nylon manufacturing, and the soil bacterium "Sphingobium" evolving an entirely new metabolic pathway that degrades the synthetic pesticide pentachlorophenol. An interesting but still controversial idea is that some adaptations might increase the ability of organisms to generate genetic diversity and adapt by natural selection (increasing organisms' evolvability).


title: Evolution

text: Adaptation occurs through the gradual modification of existing structures. Consequently, structures with similar internal organisation may have different functions in related organisms. This is the result of a single ancestral structure being adapted to function in different ways. The bones within bat wings, for example, are very similar to those in mice feet and primate hands, due to the descent of all these structures from a common mammalian ancestor. However, since all living organisms are related to some extent, even organs that appear to have little or no structural similarity, such as arthropod, squid and vertebrate eyes, or the limbs and wings of arthropods and vertebrates, can depend on a common set of homologous genes that control their assembly and function; this is called deep homology.


title: Evolution

text: During evolution, some structures may lose their original function and become vestigial structures. Such structures may have little or no function in a current species, yet have a clear function in ancestral species, or other closely related species. Examples include pseudogenes, the non-functional remains of eyes in blind cave-dwelling fish, wings in flightless birds, the presence of hip bones in whales and snakes, and sexual traits in organisms that reproduce via asexual reproduction. Examples of vestigial structures in humans include wisdom teeth, the coccyx, the vermiform appendix, and other behavioural vestiges such as goose bumps and primitive reflexes.


title: Evolution

text: However, many traits that appear to be simple adaptations are in fact exaptations: structures originally adapted for one function, but which coincidentally became somewhat useful for some other function in the process. One example is the African lizard "Holaspis guentheri", which developed an extremely flat head for hiding in crevices, as can be seen by looking at its near relatives. However, in this species, the head has become so flattened that it assists in gliding from tree to tree—an exaptation. Within cells, molecular machines such as the bacterial flagella and protein sorting machinery evolved by the recruitment of several pre-existing proteins that previously had different functions. Another example is the recruitment of enzymes from glycolysis and xenobiotic metabolism to serve as structural proteins called crystallins within the lenses of organisms' eyes.


title: Evolution

text: An area of current investigation in evolutionary developmental biology is the developmental basis of adaptations and exaptations. This research addresses the origin and evolution of embryonic development and how modifications of development and developmental processes produce novel features. These studies have shown that evolution can alter development to produce new structures, such as embryonic bone structures that develop into the jaw in other animals instead forming part of the middle ear in mammals. It is also possible for structures that have been lost in evolution to reappear due to changes in developmental genes, such as a mutation in chickens causing embryos to grow teeth similar to those of crocodiles. It is now becoming clear that most alterations in the form of organisms are due to changes in a small set of conserved genes.


title: Evolution

text: Interactions between organisms can produce both conflict and cooperation. When the interaction is between pairs of species, such as a pathogen and a host, or a predator and its prey, these species can develop matched sets of adaptations. Here, the evolution of one species causes adaptations in a second species. These changes in the second species then, in turn, cause new adaptations in the first species. This cycle of selection and response is called coevolution. An example is the production of tetrodotoxin in the rough-skinned newt and the evolution of tetrodotoxin resistance in its predator, the common garter snake. In this predator-prey pair, an evolutionary arms race has produced high levels of toxin in the newt and correspondingly high levels of toxin resistance in the snake.


title: Evolution

text: Not all co-evolved interactions between species involve conflict. Many cases of mutually beneficial interactions have evolved. For instance, an extreme cooperation exists between plants and the mycorrhizal fungi that grow on their roots and aid the plant in absorbing nutrients from the soil. This is a reciprocal relationship as the plants provide the fungi with sugars from photosynthesis. Here, the fungi actually grow inside plant cells, allowing them to exchange nutrients with their hosts, while sending signals that suppress the plant immune system.


title: Evolution

text: Coalitions between organisms of the same species have also evolved. An extreme case is the eusociality found in social insects, such as bees, termites and ants, where sterile insects feed and guard the small number of organisms in a colony that are able to reproduce. On an even smaller scale, the somatic cells that make up the body of an animal limit their reproduction so they can maintain a stable organism, which then supports a small number of the animal's germ cells to produce offspring. Here, somatic cells respond to specific signals that instruct them whether to grow, remain as they are, or die. If cells ignore these signals and multiply inappropriately, their uncontrolled growth causes cancer.


title: Evolution

text: Such cooperation within species may have evolved through the process of kin selection, which is where one organism acts to help raise a relative's offspring. This activity is selected for because if the "helping" individual contains alleles which promote the helping activity, it is likely that its kin will "also" contain these alleles and thus those alleles will be passed on. Other processes that may promote cooperation include group selection, where cooperation provides benefits to a group of organisms.


title: Evolution

text: There are multiple ways to define the concept of "species." The choice of definition is dependent on the particularities of the species concerned. For example, some species concepts apply more readily toward sexually reproducing organisms while others lend themselves better toward asexual organisms. Despite the diversity of various species concepts, these various concepts can be placed into one of three broad philosophical approaches: interbreeding, ecological and phylogenetic. The "Biological Species Concept" is a classic example of the interbreeding approach. Defined by evolutionary biologist Ernst Mayr in 1942, the BSC states that "species are groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups." Despite its wide and long-term use, the BSC like others is not without controversy, for example because these concepts cannot be applied to prokaryotes, and this is called the species problem. Some researchers have attempted a unifying monistic definition of species, while others adopt a pluralistic approach and suggest that there may be different ways to logically interpret the definition of a species.


title: Evolution

text: Barriers to reproduction between two diverging sexual populations are required for the populations to become new species. Gene flow may slow this process by spreading the new genetic variants also to the other populations. Depending on how far two species have diverged since their most recent common ancestor, it may still be possible for them to produce offspring, as with horses and donkeys mating to produce mules. Such hybrids are generally infertile. In this case, closely related species may regularly interbreed, but hybrids will be selected against and the species will remain distinct. However, viable hybrids are occasionally formed and these new species can either have properties intermediate between their parent species, or possess a totally new phenotype. The importance of hybridisation in producing new species of animals is unclear, although cases have been seen in many types of animals, with the gray tree frog being a particularly well-studied example.


title: Evolution

text: Speciation has been observed multiple times under both controlled laboratory conditions (see laboratory experiments of speciation) and in nature. In sexually reproducing organisms, speciation results from reproductive isolation followed by genealogical divergence. There are four primary geographic modes of speciation. The most common in animals is allopatric speciation, which occurs in populations initially isolated geographically, such as by habitat fragmentation or migration. Selection under these conditions can produce very rapid changes in the appearance and behaviour of organisms. As selection and drift act independently on populations isolated from the rest of their species, separation may eventually produce organisms that cannot interbreed.


title: Evolution

text: The second mode of speciation is peripatric speciation, which occurs when small populations of organisms become isolated in a new environment. This differs from allopatric speciation in that the isolated populations are numerically much smaller than the parental population. Here, the founder effect causes rapid speciation after an increase in inbreeding increases selection on homozygotes, leading to rapid genetic change.


title: Evolution

text: The third mode is parapatric speciation. This is similar to peripatric speciation in that a small population enters a new habitat, but differs in that there is no physical separation between these two populations. Instead, speciation results from the evolution of mechanisms that reduce gene flow between the two populations. Generally this occurs when there has been a drastic change in the environment within the parental species' habitat. One example is the grass "Anthoxanthum odoratum", which can undergo parapatric speciation in response to localised metal pollution from mines. Here, plants evolve that have resistance to high levels of metals in the soil. Selection against interbreeding with the metal-sensitive parental population produced a gradual change in the flowering time of the metal-resistant plants, which eventually produced complete reproductive isolation. Selection against hybrids between the two populations may cause reinforcement, which is the evolution of traits that promote mating within a species, as well as character displacement, which is when two species become more distinct in appearance.


title: Evolution

text: Finally, in sympatric speciation species diverge without geographic isolation or changes in habitat. This form is rare since even a small amount of gene flow may remove genetic differences between parts of a population. Generally, sympatric speciation in animals requires the evolution of both genetic differences and nonrandom mating, to allow reproductive isolation to evolve.


title: Evolution

text: One type of sympatric speciation involves crossbreeding of two related species to produce a new hybrid species. This is not common in animals as animal hybrids are usually sterile. This is because during meiosis the homologous chromosomes from each parent are from different species and cannot successfully pair. However, it is more common in plants because plants often double their number of chromosomes, to form polyploids. This allows the chromosomes from each parental species to form matching pairs during meiosis, since each parent's chromosomes are represented by a pair already. An example of such a speciation event is when the plant species "Arabidopsis thaliana" and "Arabidopsis arenosa" crossbred to give the new species "Arabidopsis suecica". This happened about 20,000 years ago, and the speciation process has been repeated in the laboratory, which allows the study of the genetic mechanisms involved in this process. Indeed, chromosome doubling within a species may be a common cause of reproductive isolation, as half the doubled chromosomes will be unmatched when breeding with undoubled organisms.


title: Evolution

text: Speciation events are important in the theory of punctuated equilibrium, which accounts for the pattern in the fossil record of short "bursts" of evolution interspersed with relatively long periods of stasis, where species remain relatively unchanged. In this theory, speciation and rapid evolution are linked, with natural selection and genetic drift acting most strongly on organisms undergoing speciation in novel habitats or small populations. As a result, the periods of stasis in the fossil record correspond to the parental population and the organisms undergoing speciation and rapid evolution are found in small populations or geographically restricted habitats and therefore rarely being preserved as fossils.


title: Evolution

text: Extinction is the disappearance of an entire species. Extinction is not an unusual event, as species regularly appear through speciation and disappear through extinction. Nearly all animal and plant species that have lived on Earth are now extinct, and extinction appears to be the ultimate fate of all species. These extinctions have happened continuously throughout the history of life, although the rate of extinction spikes in occasional mass extinction events. The Cretaceous–Paleogene extinction event, during which the non-avian dinosaurs became extinct, is the most well-known, but the earlier Permian–Triassic extinction event was even more severe, with approximately 96% of all marine species driven to extinction. The Holocene extinction event is an ongoing mass extinction associated with humanity's expansion across the globe over the past few thousand years. Present-day extinction rates are 100–1000 times greater than the background rate and up to 30% of current species may be extinct by the mid 21st century. Human activities are now the primary cause of the ongoing extinction event;


title: Evolution

text: The role of extinction in evolution is not very well understood and may depend on which type of extinction is considered. The causes of the continuous "low-level" extinction events, which form the majority of extinctions, may be the result of competition between species for limited resources (the competitive exclusion principle). If one species can out-compete another, this could produce species selection, with the fitter species surviving and the other species being driven to extinction. The intermittent mass extinctions are also important, but instead of acting as a selective force, they drastically reduce diversity in a nonspecific manner and promote bursts of rapid evolution and speciation in survivors.


title: Evolution

text: The Earth is about 4.54 billion years old. The earliest undisputed evidence of life on Earth dates from at least 3.5 billion years ago, during the Eoarchean Era after a geological crust started to solidify following the earlier molten Hadean Eon. Microbial mat fossils have been found in 3.48 billion-year-old sandstone in Western Australia. Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old metasedimentary rocks discovered in Western Greenland as well as "remains of biotic life" found in 4.1 billion-year-old rocks in Western Australia. Commenting on the Australian findings, Stephen Blair Hedges wrote, "If life arose relatively quickly on Earth, then it could be common in the universe." In July 2016, scientists reported identifying a set of 355 genes from the last universal common ancestor (LUCA) of all organisms living on Earth.


title: Evolution

text: More than 99 percent of all species, amounting to over five billion species, that ever lived on Earth are estimated to be extinct. Estimates on the number of Earth's current species range from 10 million to 14 million, of which about 1.9 million are estimated to have been named and 1.6 million documented in a central database to date, leaving at least 80 percent not yet described.


title: Evolution

text: Highly energetic chemistry is thought to have produced a self-replicating molecule around 4 billion years ago, and half a billion years later the last common ancestor of all life existed. The current scientific consensus is that the complex biochemistry that makes up life came from simpler chemical reactions. The beginning of life may have included self-replicating molecules such as RNA and the assembly of simple cells.


title: Evolution

text: All organisms on Earth are descended from a common ancestor or ancestral gene pool. Current species are a stage in the process of evolution, with their diversity the product of a long series of speciation and extinction events. The common descent of organisms was first deduced from four simple facts about organisms: First, they have geographic distributions that cannot be explained by local adaptation. Second, the diversity of life is not a set of completely unique organisms, but organisms that share morphological similarities. Third, vestigial traits with no clear purpose resemble functional ancestral traits. Fourth, organisms can be classified using these similarities into a hierarchy of nested groups, similar to a family tree.


title: Evolution

text: Due to horizontal gene transfer, this "tree of life" may be more complicated than a simple branching tree, since some genes have spread independently between distantly related species. To solve this problem and others, some authors prefer to use the "Coral of life" as a metaphor or a mathematical model to illustrate the evolution of life. This view dates back to an idea briefly mentioned by Darwin but later abandoned.


title: Evolution

text: Past species have also left records of their evolutionary history. Fossils, along with the comparative anatomy of present-day organisms, constitute the morphological, or anatomical, record. By comparing the anatomies of both modern and extinct species, palaeontologists can infer the lineages of those species. However, this approach is most successful for organisms that had hard body parts, such as shells, bones or teeth. Further, as prokaryotes such as bacteria and archaea share a limited set of common morphologies, their fossils do not provide information on their ancestry.


title: Evolution

text: More recently, evidence for common descent has come from the study of biochemical similarities between organisms. For example, all living cells use the same basic set of nucleotides and amino acids. The development of molecular genetics has revealed the record of evolution left in organisms' genomes: dating when species diverged through the molecular clock produced by mutations. For example, these DNA sequence comparisons have revealed that humans and chimpanzees share 98% of their genomes and analysing the few areas where they differ helps shed light on when the common ancestor of these species existed.


title: Evolution

text: Prokaryotes inhabited the Earth from approximately 3–4 billion years ago. No obvious changes in morphology or cellular organisation occurred in these organisms over the next few billion years. The eukaryotic cells emerged between 1.6 and 2.7 billion years ago. The next major change in cell structure came when bacteria were engulfed by eukaryotic cells, in a cooperative association called endosymbiosis. The engulfed bacteria and the host cell then underwent coevolution, with the bacteria evolving into either mitochondria or hydrogenosomes. Another engulfment of cyanobacterial-like organisms led to the formation of chloroplasts in algae and plants.


title: Evolution

text: The history of life was that of the unicellular eukaryotes, prokaryotes and archaea until about 610 million years ago when multicellular organisms began to appear in the oceans in the Ediacaran period. The evolution of multicellularity occurred in multiple independent events, in organisms as diverse as sponges, brown algae, cyanobacteria, slime moulds and myxobacteria. In January 2016, scientists reported that, about 800 million years ago, a minor genetic change in a single molecule called GK-PID may have allowed organisms to go from a single cell organism to one of many cells.


title: Evolution

text: Soon after the emergence of these first multicellular organisms, a remarkable amount of biological diversity appeared over approximately 10 million years, in an event called the Cambrian explosion. Here, the majority of types of modern animals appeared in the fossil record, as well as unique lineages that subsequently became extinct. Various triggers for the Cambrian explosion have been proposed, including the accumulation of oxygen in the atmosphere from photosynthesis.


title: Evolution

text: About 500 million years ago, plants and fungi colonised the land and were soon followed by arthropods and other animals. Insects were particularly successful and even today make up the majority of animal species. Amphibians first appeared around 364 million years ago, followed by early amniotes and birds around 155 million years ago (both from "reptile"-like lineages), mammals around 129 million years ago, Homininae around 10 million years ago and modern humans around 250,000 years ago. However, despite the evolution of these large animals, smaller organisms similar to the types that evolved early in this process continue to be highly successful and dominate the Earth, with the majority of both biomass and species being prokaryotes.


title: Evolution

text: The proposal that one type of organism could descend from another type goes back to some of the first pre-Socratic Greek philosophers, such as Anaximander and Empedocles. Such proposals survived into Roman times. The poet and philosopher Lucretius followed Empedocles in his masterwork "De rerum natura" ("On the Nature of Things").


title: Evolution

text: In contrast to these materialistic views, Aristotelianism had considered all natural things as actualisations of fixed natural possibilities, known as forms. This became part of a medieval teleological understanding of nature in which all things have an intended role to play in a divine cosmic order. Variations of this idea became the standard understanding of the Middle Ages and were integrated into Christian learning, but Aristotle did not demand that real types of organisms always correspond one-for-one with exact metaphysical forms and specifically gave examples of how new types of living things could come to be.


title: Evolution

text: A number of Arab Muslim scholars wrote about evolution, most notably Ibn Khaldun, who wrote the book "Muqaddimah" in 1377 AD, in which he asserted that humans developed from "the world of the monkeys", in a process by which "species become more numerous".


title: Evolution

text: The "New Science" of the 17th century rejected the Aristotelian approach. It sought to explain natural phenomena in terms of physical laws that were the same for all visible things and that did not require the existence of any fixed natural categories or divine cosmic order. However, this new approach was slow to take root in the biological sciences: the last bastion of the concept of fixed natural types. John Ray applied one of the previously more general terms for fixed natural types, "species", to plant and animal types, but he strictly identified each type of living thing as a species and proposed that each species could be defined by the features that perpetuated themselves generation after generation. The biological classification introduced by Carl Linnaeus in 1735 explicitly recognised the hierarchical nature of species relationships, but still viewed species as fixed according to a divine plan.


title: Evolution

text: Other naturalists of this time speculated on the evolutionary change of species over time according to natural laws. In 1751, Pierre Louis Maupertuis wrote of natural modifications occurring during reproduction and accumulating over many generations to produce new species. Georges-Louis Leclerc, Comte de Buffon, suggested that species could degenerate into different organisms, and Erasmus Darwin proposed that all warm-blooded animals could have descended from a single microorganism (or "filament"). The first full-fledged evolutionary scheme was Jean-Baptiste Lamarck's "transmutation" theory of 1809, which envisaged spontaneous generation continually producing simple forms of life that developed greater complexity in parallel lineages with an inherent progressive tendency, and postulated that on a local level, these lineages adapted to the environment by inheriting changes caused by their use or disuse in parents. (The latter process was later called Lamarckism.) These ideas were condemned by established naturalists as speculation lacking empirical support. In particular, Georges Cuvier insisted that species were unrelated and fixed, their similarities reflecting divine design for functional needs. In the meantime, Ray's ideas of benevolent design had been developed by William Paley into the "Natural Theology or Evidences of the Existence and Attributes of the Deity" (1802), which proposed complex adaptations as evidence of divine design and which was admired by Charles Darwin.


title: Evolution

text: The crucial break from the concept of constant typological classes or types in biology came with the theory of evolution through natural selection, which was formulated by Charles Darwin and Alfred Wallace in terms of variable populations. Darwin used the expression "descent with modification" rather than "evolution". Partly influenced by "An Essay on the Principle of Population" (1798) by Thomas Robert Malthus, Darwin noted that population growth would lead to a "struggle for existence" in which favourable variations prevailed as others perished. In each generation, many offspring fail to survive to an age of reproduction because of limited resources. This could explain the diversity of plants and animals from a common ancestry through the working of natural laws in the same way for all types of organism. Darwin developed his theory of "natural selection" from 1838 onwards and was writing up his "big book" on the subject when Alfred Russel Wallace sent him a version of virtually the same theory in 1858. Their separate papers were presented together at an 1858 meeting of the Linnean Society of London. At the end of 1859, Darwin's publication of his "abstract" as "On the Origin of Species" explained natural selection in detail and in a way that led to an increasingly wide acceptance of Darwin's concepts of evolution at the expense of alternative theories. Thomas Henry Huxley applied Darwin's ideas to humans, using paleontology and comparative anatomy to provide strong evidence that humans and apes shared a common ancestry. Some were disturbed by this since it implied that humans did not have a special place in the universe.


title: Evolution

text: The mechanisms of reproductive heritability and the origin of new traits remained a mystery. Towards this end, Darwin developed his provisional theory of pangenesis. In 1865, Gregor Mendel reported that traits were inherited in a predictable manner through the independent assortment and segregation of elements (later known as genes). Mendel's laws of inheritance eventually supplanted most of Darwin's pangenesis theory. August Weismann made the important distinction between germ cells that give rise to gametes (such as sperm and egg cells) and the somatic cells of the body, demonstrating that heredity passes through the germ line only. Hugo de Vries connected Darwin's pangenesis theory to Weismann's germ/soma cell distinction and proposed that Darwin's pangenes were concentrated in the cell nucleus and when expressed they could move into the cytoplasm to change the cell's structure. De Vries was also one of the researchers who made Mendel's work well known, believing that Mendelian traits corresponded to the transfer of heritable variations along the germline. To explain how new variants originate, de Vries developed a mutation theory that led to a temporary rift between those who accepted Darwinian evolution and biometricians who allied with de Vries. In the 1930s, pioneers in the field of population genetics, such as Ronald Fisher, Sewall Wright and J. B. S. Haldane set the foundations of evolution onto a robust statistical philosophy. The false contradiction between Darwin's theory, genetic mutations, and Mendelian inheritance was thus reconciled.


title: Evolution

text: In the 1920s and 1930s, the so-called modern synthesis connected natural selection and population genetics, based on Mendelian inheritance, into a unified theory that applied generally to any branch of biology. It explained patterns observed across species in populations, through fossil transitions in palaeontology.


title: Evolution

text: Since then, further syntheses have extended evolution's explanatory power in the light of numerous discoveries, to cover biological phenomena across the whole of the biological hierarchy from genes to populations.


title: Evolution

text: The publication of the structure of DNA by James Watson and Francis Crick with contribution of Rosalind Franklin in 1953 demonstrated a physical mechanism for inheritance. Molecular biology improved understanding of the relationship between genotype and phenotype. Advances were also made in phylogenetic systematics, mapping the transition of traits into a comparative and testable framework through the publication and use of evolutionary trees. In 1973, evolutionary biologist Theodosius Dobzhansky penned that "nothing in biology makes sense except in the light of evolution," because it has brought to light the relations of what first seemed disjointed facts in natural history into a coherent explanatory body of knowledge that describes and predicts many observable facts about life on this planet.


title: Evolution

text: One extension, known as evolutionary developmental biology and informally called "evo-devo," emphasises how changes between generations (evolution) act on patterns of change within individual organisms (development). Since the beginning of the 21st century, some biologists have argued for an extended evolutionary synthesis, which would account for the effects of non-genetic inheritance modes, such as epigenetics, parental effects, ecological inheritance and cultural inheritance, and evolvability.


title: Evolution

text: In the 19th century, particularly after the publication of "On the Origin of Species" in 1859, the idea that life had evolved was an active source of academic debate centred on the philosophical, social and religious implications of evolution. Today, the modern evolutionary synthesis is accepted by a vast majority of scientists. However, evolution remains a contentious concept for some theists.


title: Evolution

text: While various religions and denominations have reconciled their beliefs with evolution through concepts such as theistic evolution, there are creationists who believe that evolution is contradicted by the creation myths found in their religions and who raise various objections to evolution. As had been demonstrated by responses to the publication of "Vestiges of the Natural History of Creation" in 1844, the most controversial aspect of evolutionary biology is the implication of human evolution that humans share common ancestry with apes and that the mental and moral faculties of humanity have the same types of natural causes as other inherited traits in animals. In some countries, notably the United States, these tensions between science and religion have fuelled the current creation–evolution controversy, a religious conflict focusing on politics and public education. While other scientific fields such as cosmology and Earth science also conflict with literal interpretations of many religious texts, evolutionary biology experiences significantly more opposition from religious literalists.


title: Evolution

text: The teaching of evolution in American secondary school biology classes was uncommon in most of the first half of the 20th century. The Scopes Trial decision of 1925 caused the subject to become very rare in American secondary biology textbooks for a generation, but it was gradually re-introduced later and became legally protected with the 1968 "Epperson v. Arkansas" decision. Since then, the competing religious belief of creationism was legally disallowed in secondary school curricula in various decisions in the 1970s and 1980s, but it returned in pseudoscientific form as intelligent design (ID), to be excluded once again in the 2005 "Kitzmiller v. Dover Area School District" case. The debate over Darwin's ideas did not generate significant controversy in China.


title: Assyrian people

text: Assyrians are an indigenous ethnic group native to Assyria in West Asia. Modern Assyrians descend from their ancient counterparts, originating of the ancient indigenous Mesopotamians of Akkad and Sumer, who first developed the civilisation in northern Mesopotamia that would become Assyria in 2600 BCE. Assyrians have been speaking dialects of Suret, a Semitic language of the Neo-Aramaic branch, since approximately 1000 BCE. Modern Assyrians may culturally self-identify as Syriacs, Chaldeans, or Arameans for religious, geographic and tribal identification.


title: Assyrian people

text: The ancestral indigenous lands that form the Assyrian homeland are those of ancient Mesopotamia, a region currently divided between modern-day Iraq, southeastern Turkey, northwestern Iran, and northeastern Syria. A majority of modern Assyrians have migrated to other regions of the world, including North America, the Levant, Australia, Europe, Russia and the Caucasus. Emigration was triggered by tragic events such as the massacres in Hakkari, the massacres of Diyarbekır, the Assyrian genocide (concurrent with the Armenian and Greek genocides) during World War I by the Ottoman Empire and allied Kurdish tribes, the Simele massacre, the Iranian Revolution, Arab Nationalist Ba'athist policies in Iraq (between the years 1968–2003) and in Syria the take over by Islamic State of many parts in Syria and Iraq, particularly the Nineveh Plains between 2014–2017.


title: Assyrian people

text: Assyrians are almost exclusively Christian, with most adhering to the East and West Syriac liturgical rites of Christianity. The churches that constitute the East Syriac rite include the Chaldean Catholic Church, Assyrian Church of the East, and the Ancient Church of the East, whereas the churches of the West Syriac rite are the Syriac Orthodox Church and the Syriac Catholic Church. Both rites use Classical Syriac as their liturgical language.


title: Assyrian people

text: Most recently, events such as the 2003 invasion of Iraq by United States and its allies, and the Syrian civil war, which began in 2011, have displaced much of the remaining Assyrian community from their homeland as a result of ethnic and religious persecution at the hands of Islamic extremists. Of the one million or more Iraqis reported by the United Nations to have fled Iraq since the occupation, nearly 40% were the indigenous Assyrian people, even though Assyrians accounted for only around 3% of the pre-war Iraqi demography.


title: Assyrian people

text: After the emergence of the Islamic State and the taking over of much of the Assyrian homeland by the terror group, another major wave of Assyrian displacement took place. The Islamic State was driven out from the Assyrian villages in the Khabour River Valley and the areas surrounding the city of Al-Hasakah in Syria by 2015, and from the Nineveh Plains in Iraq by 2017. In 2014, the Nineveh Plain Protection Units was formed and many Assyrians joined the force to defend themselves. The organization later became part of Iraqi Armed forces and played a key role in liberating areas previously held by the Islamic State during the War in Iraq. In northern Syria, Assyrian groups have been taking part both politically and militarily in the Kurdish-dominated but multiethnic Syrian Democratic Forces (see Khabour Guards and Sutoro) and Autonomous Administration of North and East Syria.