All life forms share single genetic inheritance?

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Washington, May 17 (IANS) More than 150 years ago, Darwin proposed the theory of universal common ancestry (UCA), linking all forms of life by a shared genetic heritage from single-celled micro-organisms to humans.Until now, the theory that makes ladybugs, oak trees, champagne yeast and humans distant relatives has remained beyond the scope of a formal test.Now, a Brandeis University biochemist Douglas Theobald, reports the results of the first large scale, quantitative test of the famous theory that underpins modern evolutionary biology.The results confirm that Darwin had it right all along. In his 1859 book 'On the Origin of Species', the British naturalist proposed that 'all the organic beings which have ever lived on this earth have descended from some one primordial form'.Over the last century and a half, qualitative evidence for this theory has steadily grown, in the numerous, surprising transitional forms found in the fossil record, for example, and in the identification of sweeping fundamental biological similarities at the molecular level.According to Theobald, it doesn't really matter. 'Let's say life originated independently multiple times, which UCA allows is possible,' he said.'If so, the theory holds that a bottleneck occurred in evolution, with descendants of only one of the independent origins surviving until the present.''Alternatively, separate populations could have merged, by exchanging enough genes over time to become a single species that eventually was ancestral to us all. Either way, all of life would still be genetically related,' Theobald added.Harnessing powerful computational tools and applying specialised statistics, Theobald found that the evidence overwhelmingly supports UCA, regardless of horizontal gene transfer or multiple origins of life.Theobald said UCA is millions of times more probable than any theory of multiple independent ancestries.'There have been major advances in biology over the last decade, with our ability to test Darwin's theory in a way never before possible,' said Theobald.'The number of genetic sequences of individual organisms doubles every three years, and our computational power is much stronger now than it was even a few years ago.'While other scientists have previously examined common ancestry more narrowly, for example, among only vertebrates, Theobald is the first to formally test Darwin's theory across all three domains of life, said a Brandeis release.They include humans, yeast, and plants (whose cells have a DNA-containing nucleus) as well as bacteria and archaea (two distinct groups of unicellular micro-organisms whose DNA floats around in the cell instead of in a nucleus).Theobald studied a set of 23 universally conserved, essential proteins found in all known organisms.These findings were published in Nature.

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