Common descent

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In evolutionary biology, a group of organisms have common descent if they have a common ancestor. "There is strong quantitative support, by a formal test" for the theory that all living organisms on Earth are descended from a common ancestor.[1][2]

Charles Darwin proposed the theory of universal common descent through an evolutionary process in On the Origin of Species, saying, "There is a grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one".[3]p490

The last universal ancestor (LUA) (or last universal common ancestor, LUCA), that is viewed by evolutionary theory to be most recent common ancestor of all currently living organisms,[1] is believed to have appeared about 3.9 billion years ago.[4][5]

History[change | change source]

In the 1740s, Pierre-Louis Maupertuis made the first known suggestion that all organisms may have had a common ancestor, and that they had diverged through random variation and struggle for existence.[6][7] In Essai de Cosmologie, Maupertuis noted:


Evidence of universal common descent[change | change source]

Common biochemistry and genetic code[change | change source]

All known forms of life are based on the same fundamental biochemical organisation.

Genetic information is encoded in DNA, and transcribed into RNA, then translated into proteins by (highly similar) ribosomes, with ATP, NADH and others as energy sources, etc.

The similarities include the energy carrier adenosine triphosphate (ATP), and the fact that all amino acids found in proteins are left-handed (chirality).


The universality of this code is generally regarded by biologists as definitive evidence in favor of the theory of universal common descent. Analysis of the small differences in the genetic code has also provided support for universal common descent.[9] A statistical comparison of various alternative hypotheses has shown that universal common ancestry is significantly more probable than models involving multiple origins.[1]

Phylogenetic trees[change | change source]

Another important piece of evidence is that it is possible to construct detailed phylogenetic trees (that is, "genealogic trees" of species) mapping out the proposed divisions and common ancestors of all living species. In 2010 an analysis of available genetic data, mapping them to phylogenetic trees, gave "firm quantitative support for the unity of life. ...there is now strong quantitative support, by a formal test,[1] for the unity of life.[2]

Traditionally, these trees have been built using morphological methods, such as comparative anatomy, embryology, etc. Recently, it has been possible to construct these trees using molecular data, based on similarities and differences between genetic and protein sequences. All these methods produce essentially similar results. That phylogenetic trees based on different types of information agree with each other is strong evidence of an underlying common descent.[10]

Last Universal Ancestor[change | change source]

Some things are deduced about LUA. It was not the very first cell, but one whose descendents survived beyond the very early stages of microbial evolution. On the basis of their presence in eubacteria, archaea, and eukaryotes, about 325 proteins were present in the LUA.[11][12]

These amino acids were probably the first to be built into proteins: alanine, asparagine, aspartic acid, glycine, histidine, isoleucine, serine, threonine, and valine. These amino acids were also found in spark tube simulations,[13] and analysis of the Murchison meteorite.[14] The other amino acids, later additions to the genetic code, include several of the most complex amino acids.

References[change | change source]

  1. 1.0 1.1 1.2 1.3 Theobald, Douglas L. (2010). "A formal test of the theory of universal common ancestry". Nature 465 (7295): 219–222. doi:10.1038/nature09014. PMID 20463738. 
  2. 2.0 2.1 Steel, Mike; Penny, David (2010). "Origins of life: common ancestry put to the test". Nature 465 (7295): 168–9. doi:10.1038/465168a. PMID 20463725. 
  3. Darwin, Charles; Costa, James T. 2009. The Annotated Origin: a facsimile of the first edition of On the Origin of Species, annotated by James T. Costa. Cambridge, Massachusetts: Belknap Press of Harvard University. ISBN 978-0-674-03281-1
  4. Doolittle, W.F (February 2000). "Uprooting the tree of life". Scientific American 282 (6): 90–95. doi:10.1038/scientificamerican0200-90. PMID 10710791. 
  5. Glansdorff, N; Xu, Y; Labedan, B (2008). "The last universal common ancestor: emergence, constitution and genetic legacy of an elusive forerunner.". Biology direct 3 (1): 29. doi:10.1186/1745-6150-3-29. PMC 2478661. PMID 18613974. 
  6. J.S. Bromley 1970. The new Cambridge modern history: The rise of Great Britain and Russia, 1688-1715/25 CUP Archive. ISBN 978-0-521-07524-4, pgs. 62-63.
  7. Geoffrey Russell Richards Treasure 1985. The making of modern Europe, 1648-1780, Taylor & Francis ISBN 978-0-416-72370-0 p142
  8. C. Leon Harris 1981. Evolution, genesis and revelations, with readings from Empedocles to Wilson, SUNY Press. ISBN 978-0-87395-487-7 p107
  9. Knight, Robin, et al. (2001). "Rewiring the keyboard: evolvability of the genetic code". Nature Reviews Genetics 2 (1): 49–58. doi:10.1038/35047500. PMID 11253070. 
  10. Theobald, Douglas (2004). "Prediction 1.3: Consilience of independent phylogenies". 29+ Evidences for Macroevolution. TalkOrigins Foundation. Retrieved November 20, 2009.
  11. Brooks, Dawn J. et al 2002. Evolution of amino acid frequencies in proteins over deep time: inferred order of introduction of amino acids into the genetic code. Molecular Biology and Evolution 19, 1645-1655. [1]
  12. Kyrpides N; Overbeek R. & Ouzounis C. 1999 Universal protein families and the functional content of the last universal common ancestor. J. Mol. Evol 49:413-423
  13. Miller S.L. 1953 Production of amino acids under possible primitive earth conditions. Science 117:528-529
  14. Kvenvolden K. et al 1970 Evidence for extraterrestrial amino-acids and hydrocarbons in the Murchison meteorite Nature 228:923.