One evolving species vs speciation.

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:

---

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.

---

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

Perhaps this was one of the many times you argued with me about a position I have never held. No, it is to suggest that adaptive selection in a population is not sufficient to produce speciation. Certainly, but the author is clearly not claiming that the existence of a barrier to gene flow is speciation, otherwise putting two populations in separate sealed containers would be an example of speciation.To simplify the terms the author suggests that a reduction in gene flow is necessary, though not necessarily sufficient, for speciation to occur and that natural selection is not sufficient for speciation to occur. I don't think he goes further than positing a block to gene flow as the precipitating event leading towards speciation, certainly not as far as ruling out any other contributing factor.So I agree with what you said but I don't see any basis for thinking that the original author would have disagreed with it.TTFN,WK

So, do the two words I remembered from my high school biology text book impressed you now?

---

Disclaimer:

​

Occasionally, owing to the deficiency of the English language, I have used he/him/his meaning he or she/him or her/his or her in order to avoid awkwardness of style.

​

He, him, and his are not intended as exclusively masculine pronouns. They may refer to either sex or to both sexes!

So, to head back towards the question from the OP...Is there a reasonable scenario for Humans to become split and isolated over a period of time long enough to result in two separate species other than our moving off world?

---

Aslan is not a Tame Lion

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

I'd say yes, for a given value of reasonable. The most obvious 'reasonable' scenario would be some global cataclysm knocking people back to the stone age in technological terms and leaving only a few isolated groups in distant locations. The reasonableness of such a scenario is highly dependent on how long it would take such populations to reach a technological level allowing them to make substantial sea voyages, i.e. trans-atlantic/pacific. A lot of current theories seem to suggest the required level is 'not all that much'.TTFN,WK

But since we have examples of atleast two such scenarios, the original dispersal and whatever events led to the bottlenecks seen in the genetic record that did not lead to speciation, how reasonable is that?The second consideration is that even in such a scenario, today there is the knowledge that there are other humans in other areas that would help drive attempts at travel.Edited by jar, : appalin spallin

---

Aslan is not a Tame Lion

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

Taz, this scenario has actually occurred. When the Londoners built their underground subway in the 1880's, some of the prevalent surface mosquitos - Culex pipiens - flew down into the tunnels and were trapped there. Exposed to a radically different environment, constant dim lighting, uniform temperature, no seasonal changes, etc., they evolved (by drift and adaptation) to a new species: Culex molestans. While C. pipiens feeds almost exclusively on bird blood, C. molestans evolved a preference for human blood (hence its name). Pipiens and molestans do not interbreed and thus became distinct species in less that a century (I don't know how many generations that is).The great theologian Joseph Smith taught that the interior of the earth is hollow and inhabited by a people that live on the inside surface of the earthly shell - and he must be correct since he was told this by an angle of god.. (Apparently, the inner surface people invented Velcro long before we did.) He also taught that there is a hole at the north pole through which we could enter that inner world. Now that the polar ice cap is disappearing, we should be able to enter that world and test if that inner population is reproductively isolated from us outer surface critters. Genetic analysis should determine if and when our two groups separated.

Are you talking about what I described in the first example in the OP? I can certainly see the technical possibility of something like that happening, either from the rich choosing some particular trait or from some despotic power imposing some trait.Speciation as policy or fad.

---

Aslan is not a Tame Lion

Probably 100 generations, considering they breed yearly. There have been legends of bottomless holes that would open up and then close in a short time later. Supposedly, some people have thrown objects, including fire sticks, down the hole and they never touched the bottom so that's why they concluded that these holes were bottomless.Anyhow, I wonder if Smith had anything to do with these myths.

---

Disclaimer:

​

Occasionally, owing to the deficiency of the English language, I have used he/him/his meaning he or she/him or her/his or her in order to avoid awkwardness of style.

​

He, him, and his are not intended as exclusively masculine pronouns. They may refer to either sex or to both sexes!

I was going to refute your original refutation of my use of "gene flow" but I quickly realized that I didn't have the sufficient knowledge to clear it up precisely. So, I just decided to wait for some fool to clear it up for me.See, it's one of those things that I know just enough to apply it to my everday conversation but not enough to do a lecture on.

---

Disclaimer:

​

Occasionally, owing to the deficiency of the English language, I have used he/him/his meaning he or she/him or her/his or her in order to avoid awkwardness of style.

​

He, him, and his are not intended as exclusively masculine pronouns. They may refer to either sex or to both sexes!

Folk, the thread is on Human speciation, not mosquitos.

---

Aslan is not a Tame Lion