Early embryology; clockwork construction plan (Introduction)

by dhw, Thursday, October 20, 2011, 15:53 (4783 days ago) @ David Turell

Dhw: It all brings me back to one of my hobbyhorses. Once we strip the word “mutations” of its association with “randomness”, isn’t this a view of evolution that might be acceptable on both sides of the fence? The theist can carry on claiming that the mutations have been coded into the Hox mechanism (or the UI has intervened), while the atheist can carry on claiming that they have come about through chance and/or environmental pressures.

DAVID: Your hobbyhorse creates more problems if it backs up. Where in the world would a master Hox gene come from to coordinate the formation of a single-celled organism to launch life? The genes we have now started somehow! I don't think I've seen a paper describing a Hox gene for epigenetic changes to the genome, but just what does control that area of genome activity?

All hobbyhorses create problems if they back up! But I’m only trying to follow through your own speculation that the “jumps” that lead to new species might have come about through a “major coordinated set of changes in the Hox genes.”

My (extremely amateur) speculation doesn’t concern a Hox gene for epigenetic changes, but the exact reverse. We know that epigenetic changes occur in response to changes in the environment. According to Wikipedia, dietary changes in mice have been seen to affect expression of the agouti gene (influencing fur colour and weight), and “more than 100 cases of epigenetic transgenerational inheritance phenomena have been reported in a wide range of organisms, including prokaryotes, plants and animals.” If environmental changes could affect one gene, why not others (Hox)? You say that “the genes we have now started somehow!” The same applies to all the complex organs we have now. And if the Hox genes plan organ systems and structures, they would appear to be the obvious “breeding ground” for innovative organs and, ultimately, new species. If there really was a link to epigenetic changes, wouldn’t this vastly reduce the unlikely role of chance? I’m talking only of evolution, not of the origin of life or of the mechanisms themselves, and I’m asking because I’m in no position to judge the feasibility of such speculation. So please feel free to shoot me down if it’s all nonsense.