“Much of what living cells do is carried out by “molecular machines” – physical complexes of specialized proteins working together to carry out some biological function. How the minute steps of evolution produced these constructions has long puzzled scientists, and provided a favorite target for creationists.”
Groups of molecules that happen to stick are credited with tinkering, degradation, and good luck during evolution. Does that mean each of our ancestors as far back as single-celled organisms was preserved because they helped our other ancestors to survive? If so, I have a problem with what appears to be a one-way model. For example, how does the accumulation of simple, degenerative changes over long periods of times cause speciation, which incorporates many of the complex molecular machines present in organisms today? I think the accumulation of simple, degenerative changes in different organisms must stop for one species to establish its ecological niche but I don’t see any explanation for stop-and-start degenerative changes. That’s why one-way models of evolved complexity don’t work for me, but especially when the “one way” is via degradation. For contrast, Lynch et al find no evidence for stepwise evolution.
“There is a broad consensus that many of the genetic changes underlying the evolution of morphology occur by the stepwise modification of individual pre-existing cis-regulatory element modules5,6,29. However, it is questionable whether the origin of complex novelties—such as the origin of new cell types, which involves the recruitment of hundreds of genes—can be achieved by these small-scale changes7,29.”
The importance of the evolved mammalian placenta to human behavior cannot be overstated. The chemical communication that occurs in utero between mother and child probably are responsible for the genetically predisposed mother-infant bond, which sets the post-natal stage for the development of differences in adult behavior. I will have more to say about this in a follow-up post.