Evidence for the Last Universal Common Ancestor (LUCA)
by, 28th June 2012 at 04:07 PM (1513 Views)
Evolution via natural selection is almost universally accepted amongst scientists as the explanation for the diversity of life on Earth. Evolution by natural selection, in the century and a half since it's introduction by Charles Darwin, has served as the foundation of our understanding of life and its processes. From modern medicine to molecular biology, evolution has been perhaps the most powerful tool of scientific understanding ever developed.
Defined by Charles Darwin as the "principle by which each slight variation [of a trait], if useful, is preserved," natural selection has been perhaps the most important scientific discovery of all time.
It has never been falsified. With growing understanding of the complex molecular machinery in cells, to the understanding of heritable and learned behaviors and traits, evolutionary biology has changed a lot since the time of Darwin. But his theory - at it's basic and succinct level, has never been falsified.
With that said, one of the common tactics employed by doubters of the veracity of evolutionary theory is to suggest that there's little or no evidence for the common life form from which the diversity of life sprang. This life form, termed the Last Universal Common Ancestor (LUCA), is thought to have existed between 3 and 4 billion years ago.
And there is evidence for it:
The common fundamental biochemical structure to all known life forms - that is, much of the machinery used in replicating DNA (or RNA, for that matter) and synthesizing proteins are homologous even between highly divergent life forms. The translation of nucleic acid sequences into proteins utilizes a highly similar triplet codon sequencing amongst all known life forms, from bacteria to humans.
It's now generally accepted that all life evolved from the LUCA. There is still ongoing debate about what, exactly, the LUCA "looked," like - whether it was a thermophile or mesophile, whether its genetic material was sequestered into a protonucleus or not.
However, I submit that there is absolutely no reasonable doubt that all life evolved from a universal common ancestor. That evolution alone is sufficient to explain the diversity of life on earth. And that one day - perhaps soon - we will know and understand the characteristics of this common ancestor.
**Addendum: Further evidence available upon request. Furthermore, anyone wishing to have copies of any articles linked to, if unable to access them, is free to send me a message and I will send a .pdf of the article.0 Thanks, 0 Likes, 0 Dislikes
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