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{{See also|History of evolutionary thought}}
The idea that all living things (including things considered non-living by science) are related is a recurring theme in many indigenous worldviews across the world.<ref>{{Cite web|last=Staff|first=I. C. T.|title=We Are All Related: Indigenous Knowledge Reaffirmed by Digitized Tree of Life|url=https://indiancountrytoday.com/archive/we-are-all-related-indigenous-knowledge-reaffirmed-by-digitized-tree-of-life|access-date=2021-05-05|website=Indian Country Today|date=13 September 2018 |language=en}}</ref> Later on, in the 1740s, the French [[mathematician]] [[Pierre Louis Maupertuis]] arrived at the idea that all organisms had a common ancestor, and had diverged through random variation and [[natural selection]].<ref>{{harvnb |Crombie |Hoskin |1970 |pp=[https://books.google.com/books?id=OOgzAAAAIAAJ&dq=Maupertuis+%22for+the+first+time%22&pg=PA62 62–63]}}</ref><ref>{{harvnb |Treasure |1985 |p=142}}</ref> In ''Essai de cosmologie'' (1750), Maupertuis noted:
<blockquote>May we not say that, in the fortuitous combination of the productions of Nature, since only those creatures ''could'' survive in whose organizations a certain degree of adaptation was present, there is nothing extraordinary in the fact that such adaptation is actually found in all these species which now exist? Chance, one might say, turned out a vast number of individuals; a small proportion of these were organized in such a manner that the animals' organs could satisfy their needs. A much greater number showed neither adaptation nor order; these last have all perished.... Thus the species which we see today are but a small part of all those that a blind destiny has produced.<ref>{{harvnb |Harris |1981 |p=[https://books.google.com/books?id=Fkqg3TIkBJwC&dq=Essai+de+Cosmologie+%22blind+destiny%22&pg=PA107 107]}}</ref></blockquote>
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The [[genetic code]] (the "translation table" according to which DNA information is translated into [[amino acid]]s, and hence proteins) is nearly identical for all known lifeforms, from [[bacteria]] and [[archaea]] to [[animal]]s and [[plant]]s. The universality of this code is generally regarded by biologists as definitive evidence in favor of universal common descent.<ref name=Knight/>
The way that [[Genetic code|codon]]s (DNA triplets) are mapped to [[amino acid]]s seems to be strongly optimised. Richard Egel argues that in particular the [[hydrophobic]] (non-polar) side-chains are well organised, suggesting that these enabled the earliest organisms to create [[peptide]]s with water-repelling regions able to support the essential electron exchange ([[redox]]) reactions for energy transfer.<ref name=Egel>{{cite journal |last1=Egel |first1=Richard |title=Primal Eukaryogenesis: On the Communal Nature of Precellular States, Ancestral to Modern Life |journal=Life |date=March 2012 |volume=2 |issue=1 |pages=170–212 |doi=10.3390/life2010170 |pmc=4187143 |pmid=25382122|bibcode=2012Life....2..170E |doi-access=free }}</ref>
===Selectively neutral similarities===
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