One evolving species vs speciation.

Taz, isn't the scenario you decribe as gene flow really random genetic drift ?”HM

You're right about the scenario that Taz postulates. He describes one population drifting into two. Stiil, I don't see why gene flow needs special mention. The evolutionary force in his scenario is drift, not flow. Gene flow might happen eventually, however, after all the drifted alleles are fixed in each of the new populations.”HM

After a little googling I found plenty of references to support your point. I think you win on that one.”HM

Well, maybe it doesn't, given my capitulation to PaulK in the previous post. I was reacting to this statement:

quote:

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Species aren't formed by selection for differing adaptive traits within a population, but by the interruption of the gene flow that is caused by migration or invasion between populations.

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I think species can be formed by multiple mechanisms, not all of which are selective, as I have argued with you before in other threads. I've even posted this schematic to illustrate the different ways speciation (or macroevolution) can occur: To argue that "species aren't formed by selection for differing adaptive traits within a population" is to ignore the role of natural selection. To argue that speciation occurs via "the interruption of the gene flow that is caused by migration or invasion between populations" is OK, but narrow. Other "forces" in addition to gene flow play their parts in speciation, too. Don't you agree?”HM

I must admit I did not know that gene flow was a significant abatement to drift. But it makes sense to me now. So I'm backing off this one with appologies to you, PaulK, and mbg for being Pb headed.”HM

Rub it in. Rub it in.”HM

After thinking it over, I can't visualize one. Now I'm wondering if humans would even need to become split and isolated in order to speciate. Couldn't new alleles arrive naturally from mutation, or artificially from deliberate insertion, to survive (in rare cases) and become fixed in a population without the need for the drift-flow competition? Couldn't natural selection follow on from there to force a speciation? But whether or not this would work in the human population, I really don't know. Some say we will evolve more artificially than naturally. Maybe our own genetic engineering will be how we eventually speciate. Would that be considered a form of gene flow?”HM

Are you familiar with Thomas Gold's "Deep Hot Biosphere"? It's right up your alley, except Gold is quite serious about thermophilic prokaryotes living in a deep, hot biosphere. His book on that suject is a favorite of mine.”HM