scientific study life existed prior including start roughly years present includes study fossils determine organisms evolution interactions environments observations documented far 5th century science established 18th century result work comparative anatomy developed rapidly 19th century term originates greek old ancient creature speech thought study lies border biology geology differs study modern humans uses techniques drawn wide range sciences including mathematics engineering use techniques enabled discover evolutionary history life way earth capable supporting life million years ago knowledge increased developed specialised sub divisions focus different types fossil organisms study ecology environmental history ancient climates body fossils trace fossils principal types evidence ancient life evidence helped evolution life organisms large leave body fossils estimating dates remains essential difficult adjacent rock layers allow dating provides absolute dates accurate rely relative dating solving puzzles classifying ancient organisms difficult fit taxonomy commonly classifying living organisms use draw evolutionary family trees final quarter 20th century saw development molecular investigates closely organisms related measuring similar dna molecular estimate dates species diverged controversy reliability molecular clock estimates depend overview simplest definition study ancient life seeks information aspects past organisms identity origin environment evolution tell earth organic past historical science historical sciences geology astronomy history means aims describe phenomena past reconstruct causes main elements description phenomena developing general theory causes types change applying theories specific facts trying explain past phenomena historical scientists construct set causes look smoking gun piece evidence indicates hypothesis better explanation smoking gun discovered fortunate accident research example discovery rich layer cretaceous boundary impact favored explanations cretaceous extinction event main type science experimental science said work conducting experiments workings causes natural phenomena note approach confirm hypothesis correct later experiment confronted totally unexpected phenomena evidence invisible radiation experimental scientists use approach historical scientists construct set causes look smoking gun related sciences lies boundary biology geology focuses record past life main source evidence fossils found rocks historical reasons geology departments universities 19th century early 20th century geology departments found evidence important estimating ages rocks biology departments showed little interest overlap primarily works objects humans human remains interested characteristics evolution humans organisms dealing evidence humans archaeologists work example identify animal plant fossils archaeological site discover people lived ate analyze climate time site inhabited humans addition uses techniques derived sciences including biology ecology chemistry physics mathematics example signatures rocks help discover life arose earth analyses carbon help identify climate changes explain major transitions extinction event relatively recent discipline molecular helps comparisons different modern organisms dna construct evolutionary family trees estimate dates important evolutionary developments approach controversial doubts reliability molecular clock techniques developed engineering ancient organisms worked example fast powerful bite relatively commonplace study fossils ray combination biology study casts species related humans learn evolution human brains contributes investigation possible life planets developing models life arisen providing techniques detecting evidence life subdivisions knowledge increased developed specialised subdivisions fossils earliest fish immediate ancestors modern mammals deals fossils invertebrates worms focuses study fossil plants traditionally includes study fossil algae fungi study spores produced land plants border deals living fossil organisms deals microscopic fossil organisms regardless group belong instead focusing individual organisms examines interactions different organisms places food chains way interaction organisms environment example development bacteria hugely increased productivity diversity ecosystems caused atmosphere evolution complex cells organisms built treated focuses history earth climate mechanisms changed included evolutionary developments example rapid expansion land plants period removed carbon dioxide atmosphere reducing greenhouse effect helping cause ice age period use fossils work chronological order rocks formed useful studies spatial distribution organisms linked geology explains earth geography changed time body fossils fossils organisms bodies usually type evidence common types wood bones shells rare event fossils destroyed erosion observed fossil record incomplete increasingly time despite adequate illustrate broader patterns life history fossil record different environments favorable preservation different types organism parts organisms parts organisms usually preserved shells animal species soft bodied decay result plus living animals thirds found fossils occasionally unusual environments preserve soft tissues allow examine internal anatomy animals sediments represented shells spines claws etc preserved present incomplete picture life time majority organisms living time probably represented restricted narrow range environments soft bodied organisms preserved quickly events mudslides exceptional events cause quick burial difficult study normal environments animals fossil record means organisms expected exist long found fossil record known effect trace fossils trace fossils consist mainly tracks include fossil marks left feeding trace fossils particularly significant represent data source limited animals easily hard parts reflect organisms traces date significantly earlier body fossils animals thought capable making whilst exact assignment trace fossils makers generally impossible traces example provide earliest physical evidence appearance moderately complex animals comparable observations observations help global level biological activity affinity certain fossils example features rocks reveal life arose earth provide evidence presence cells type organisms built analyses carbon help explain major transitions extinction event classifying ancient organisms naming groups organisms way clear widely agreed important disputes based names taxonomy commonly classifying living organisms runs difficulties dealing newly discovered organisms significantly different known ones example hard decide level place new higher level grouping genus family order important rules naming groups tied levels group moved different level renamed generally use approaches based technique working evolutionary family tree set organisms works logic groups similarities group closely related characters compared presence molecular comparing sequences dna proteins result successful analysis hierarchy groups share common ancestor family tree branches leading junction little information achieve junctions branches technique features wings camera eyes evolved taken account analyses evolutionary developmental biology commonly abbreviated helps produce family trees understand fossils example development modern suggests descendants extinct period estimating dates organisms seeks map living things changed time substantial aim difficulty working old fossils beds preserve fossils typically lack radioactive elements needed dating technique means giving rocks greater million years old absolute age accurate better dating requires careful laboratory work basic principle simple rates radioactive elements decay known ratio radioactive element element shows long ago radioactive element incorporated rock radioactive elements common rocks volcanic origin fossil bearing rocks dated volcanic ash layers consequently usually rely date fossils science layer cake record compared puzzle rocks normally form relatively horizontal layers layer younger underneath fossil found layers ages known fossil age lie known ages rock sequences continuous broken faults periods erosion difficult match rock beds directly fossils species survived relatively short time link isolated rocks technique called instance short range period rocks unknown age found traces mid age index fossils distinctive globally distributed short time range useful misleading results produced index fossils turn longer fossil ranges thought general provide relative dating sufficient studying evolution difficult time periods problems involved matching rocks age different continents family tree relationships help narrow date appeared instance fossils date million years ago calculated family tree says ancestor evolved million years ago possible estimate long ago living diverged approximately long ago common ancestor lived assuming dna accumulate constant rate molecular provide approximate timing example sufficiently precise reliable estimating groups feature explosion evolved estimates produced different techniques vary factor overview history life evolutionary history life stretches million years ago possibly far million years ago earth formed million years ago collision formed moon million years later cooled quickly oceans atmosphere million years ago evidence million years ago likely bombardment struck earth time atmosphere oceans stripped away oldest clear evidence life earth dates million years ago reports disputed fossil bacteria million years ago evidence presence life million years ago scientists proposed life earth seeded research explanations life arisen independently earth million years multi layered colonies different types bacteria dominant life earth evolution enabled play major role atmosphere million years ago change atmosphere increased effectiveness evolution cells complex internal structures present earlier evolution acquired ability transform oxygen poison powerful source energy innovation come primitive capturing oxygen powered bacteria transforming called earliest evidence complex dates million years ago life composed cells earliest evidence million years ago cells different functions appears million years ago possible fungus million years ago probable red sexual reproduction cells organism risk taken rogue cells retain ability reproduce earliest known animals million years ago modern looking earliest animals appeared early fossils animals rare develop hard parts easily million years ago earliest modern looking animals appear early weird wonders bear little obvious resemblance modern animals long running debate explosion truly rapid period evolutionary experimentation alternative views modern looking animals began evolving earlier fossils found weird wonders evolutionary cousins modern groups remained obscure group fish jaws appeared late spread life water land required organisms solve problems including protection drying supporting gravity earliest evidence land plants land invertebrates date million years ago million years ago respectively lineage produced land evolved later rapidly million years ago million years ago recent discoveries overturned earlier ideas history driving forces evolution land plants successful caused ecological crisis evolution spread fungi digest dead wood period including ancestors mammals dominated land environments extinction event million years ago came close complex life apparently fairly sudden slow recovery previously obscure group abundant diverse terrestrial group dominant land rest birds evolved group time mammals ancestors survived small mainly nocturnal apparent set accelerated development traits hair cretaceous extinction event million years ago killed non birds surviving mammals increased rapidly size diversity took air sea fossil evidence indicates flowering plants appeared rapidly early cretaceous million years ago million years ago rapid rise dominance terrestrial ecosystems thought propelled insects social insects appeared time account small parts insect family tree form total mass insects humans evolved lineage upright walking earliest fossils date million years ago early members lineage sized brains big modern humans signs steady increase brain size million years ago long running debate modern humans descendants single small population africa migrated world years ago replaced previous species arose worldwide time result mass life earth suffered occasional mass million years ago disasters time mass accelerated evolution life earth dominance particular ecological passes group organisms rarely new dominant group superior old usually extinction event old dominant group makes way new fossil record appears rate extinction slowing gaps mass longer average background rates extinction decreasing certain actual rate extinction altered observations explained ways oceans life million years vulnerable mass dissolved oxygen widespread penetrated greater depths development life land reduced run nutrients risk events marine ecosystems food chains likely disrupted reasonably complete fossils rare extinct organisms represented partial fossils complete fossils oldest rocks mistakenly assigned parts organism different genera defined solely accommodate finds story example risk mistake higher older fossils unlike parts living organism genera represented fragments found genera appear extinct quickly biodiversity fossil record number distinct genera alive given time occurrence occurrence time shows different trend fairly swift rise million years ago slight decline million years ago devastating extinction event important factor swift rise million years ago present history established earlier noticed aspects fossil record ancient greek philosopher concluded fossil sea shells areas land water middle ages persian naturalist known europe discussed fossils proposed theory albert elaborated 14th century chinese naturalist proposed theory climate change based presence bamboo regions time dry bamboo early modern europe systematic study fossils emerged integral changes natural philosophy occurred age reason significant contributions field designed numerous fossils end 18th century work established comparative anatomy scientific discipline proving fossil animals resembled living ones demonstrated animals extinct leading emergence expanding knowledge fossil record played increasing role development geology particularly half 19th century saw geological activity increasingly organised growth societies museums increasing number professional fossil specialists interest increased reasons purely scientific geology helped find exploit natural resources coal contributed rapid increase knowledge history life earth progress definition time scale largely based fossil evidence marie editor coined word refer study ancient living organisms fossils knowledge life history continued improve increasingly obvious kind successive order development life encouraged early evolutionary theories species published focus shifted understanding evolutionary paths including human evolution evolutionary theory half 19th century saw tremendous expansion activity especially north_america trend continued 20th century additional regions earth opened systematic fossil collection fossils found china near end 20th century particularly important provided new information earliest evolution animals early fish evolution birds decades 20th century saw renewed interest mass role evolution life earth renewed interest explosion apparently saw development body plans animal discovery fossils developments extended knowledge history life far increasing awareness pioneering work led development population mid-20th century modern evolutionary synthesis explains evolution outcome events horizontal gene transfer provide genetic variation genetic drift natural selection driving changes variation time years role operation dna genetic inheritance discovered leading known central molecular biology 1960s molecular investigation evolutionary family trees techniques derived began impact particularly proposed human lineage diverged recently generally thought time early study compared proteins humans molecular research based comparisons dna
Paleontology