Proving common descent (Introduction)

by dhw, Sunday, November 04, 2012, 17:58 (4403 days ago) @ David Turell

DAVID: The eyes have it. Genetic traces of opsin production show the descent pattern. First opsin without function, then functional, then all sorts of eyes:-http://online.wsj.com/article/SB10001424052970204840504578086700901693588.html?mod=WSJ_...-Thank you for this article and your useful summary. Let's assume this is indeed what happened, i.e. "that vision was a single evolutionary innovation", and that all sorts of eyes then developed from the original prototype. Two questions: why, and how?-First why. If the initial mechanism was useful, what need was there for it to improve, let alone to vary? (Of course the same question can be asked about bacteria.)-"The common ancestor of ourselves and the placozoa duplicated a gene and changed one of the copies into a recognizable opsin." 
"The common ancestor of ourselves, insects and jellyfish made the change to light detection, then experienced two more duplications...to give the three kinds of light-sending opsins we still possess today."-How? "Duplicated and changed", "made the change", "experienced...". We're not talking of the same eye gradually improving because short-sighted oojahs were soon wiped out and only the best-sighted oojahs survived (= improvement by natural selection). We're talking about DIFFERENT eyes.
 
Here's a suggestion (you are allowed to yawn): that innovation is caused by experimentation between cells/cell communities, and once a combination turns out to be functional and advantageous, further experimentation follows ... not by random mutation but by intercellular cooperation.
 
The single innovation "is a discovery that would have surprised an earlier generation of evolutionary biologists, who contrasted the compound eye of the insect with the camera-like eye of human beings and imagined several parallel inventions."-I would suggest that both theories are correct: first the single invention, then later, parallel inventions ... all engineered in exactly the same way as A first invented the wheel, then B, C, D invented different combinations of wheels. Once we accept the innate intelligence of the mechanism (regardless of the ultimately all-important question of how it got there originally), everything else fits into place.