2/17/2010 | Share this article: View CommentsBy Best0fScience --
In evolutionary biology, a group of organisms have common descent if they have a common ancestor. All living organisms on Earth are descended from a common ancestor or ancestral gene pool.
Image via WikipediaCharles Darwin proposed his theory of universal common descent through an evolutionary process in his "On the Origin of Species" (1859), and later in "The Descent of Man" (1871). This theory is now widely accepted by biologists.
The last universal ancestor (LUA) (or last universal common ancestor, LUCA), that is, the most recent common ancestor of all currently living organisms, is believed to have appeared about 3.9 billion years ago.
In "The Ancestor's Tale", Richard Dawkins coined the word concestor, as a substitute for common ancestor or most recent common ancestor. This new word is very gradually entering scientific parlance.
Common biochemistry and genetic code: All known forms of life are based on the same fundamental biochemical organisation: genetic information encoded in DNA, transcribed into RNA, through the effect of protein- and RNA-enzymes, then translated into proteins by (highly similar) ribosomes, with ATP, NADH and others as energy sources, etc.
Furthermore, the genetic code (the "translation table" according to which DNA information is translated into proteins) is nearly identical for all known lifeforms, from bacteria to humans.
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.
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