Re: Mara -- reply to come -- now, here
Posted by Ben on Jun 27, 2002 at 15:05
Re: Mara -- reply to come -- now, here (Sparrow)
Biologists have been aware of the frequency of Lateral Gene Transfer in microorganisms for quite a while, and what that would naturally imply as to the history of evolution of single celled organisms.
Larger organisms, especially sexual organisms, have longer reproduction cycles, and a larger set of dependent genes which do not typically repond well to random lateral gene transfers. In addition to this, metazoa tend to have skins or other membranes which protect them from invasion by the massive hosts of other bacteria (viri being a notable exception).
Microorganisms, on the other hand, reproduce so rapidly and have a somewhat simpler system which makes gene transfer inevitable. So we are faced with the fact that though there is "probably" a common ancestor deep down there somewhere, the incestuous nature of gene transfers between these groups of cells would all but eliminate the evidence.
But of course, nobody said that "all" life must come from a single common ancestor for evolution to be the explanation for the similarity between all multicellular life. Even after reading this article, which is still absolutely Darwinian in nature even though the headline says otherwise, it is still very unlikely that the very first cells evolved spontaneously at the same time from the pre-cellular chemical (probably RNA) metabolisms.
Unique positive mutations are rare, and tend to be made in one place, and then spread through selection, or in the case of microorganisms through lateral gene transfer. This is still solidly Darwinian evoution, though the mechanism of gene distribution may be a little different.
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