On 08/12/2010 02:40 PM, Alberto G. Corona wrote:

A change to a gene does not make you to have a extra bone. It can make you to have your hand slighltly longer. or shorter.

Actually I suspect it does - or at least can do. It's just a rather rare event.

In fact there are metalevels of selection that discard abrupt changes. For example, when females ovulate there are a strong selection where thounsands of candidate cell ovules are tested and discarded. This is one of the reasons why anomalous mutations are scarce.

I won't claim to be an expert in genetics, but I was under the impression that "big" changes to an organism's genetic code are usually fatal. This is the mechanism that "discards" any "abrupt" changes; they tend to not work properly. The situation is a little different with evolving computer programs, since it isn't the computer program itself that makes the copies, it's some external entity "analysing" the programs and "deciding" which ones to copy. Random example: Most animals can synthesize vitamin C. But humans and a handful of other related species can't. We have the whole metabolic pathway, it's all there, it's still working, except that the gene for the final enzyme in the sequence is busted. The enzyme transcribed from it doesn't actually work at all. Now, if you were born with a busted rhodopsin gene, you'd be blind, and probably wouldn't remain alive very long. However, since the stuff we eat has a fair amount of vitamin C in it anyway, apparently being biologically incapable of synthesizing it isn't actually a very big deal. (Unless you try to sail across the Atlantic Ocean...) Thus, almost nobody inherits a busted rhodopsin gene, but the entire human species has inherited a knackered L-gulonolactone oxidase enzyme. Make of that what you will...