How many generations does speciation take?

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It's not that I doubt evolution occurs, we certainly went from populations of single celled organisms to our current state of biodiversity, but I'm really beginning to question HOW it occurs; specifically, the common explanations of how it occurs which I encounter in this forum daily. These explanations are beginning to seem simplistic to me and smack of ignorance of the actual process, and, yes, even 'faith' in a process that isn't nearly as well understood as one would think reading some of these threads.

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The conditions for each instance of speciation is different. Using a really poor analogy that probably only makes sense to me, speciation is an analog process instead of a digital process (I bet McFall get's this one though). Perhaps meteorology is a better analogy. We know the forces that go into cloud formation, hurricanes, etc. However, we can't predict long term patterns with any specificity because the forces in motion are not amenable to modeling. It comes down to the randomness of mutations, the randomness of environmental changes, and the inherent chaos that our universe is in. Explanations are simplistic because the specifics are always different. The effects of speciation are consistent, but the causes of speciation are always complicated and inconsistent.All of this came to me when I was trying to think of an answer for the OP. I think it is impossible to calculate speciation rates with any accuracy. Any model hits the old wall of "the map is not the territory". Every model is going to be insufficient, at least in my opinion. I think it is a topic worthy of consideration and debate, but in the end I think it will be a Fool's Errand. And as we all know, I am always right.

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This is a good answer, yet I still hear you saying "we know that evolution occurs, but we can't actually predict when it will occur, how it will occur, why it doesn't occur when, where, or how we expect it to, etc."

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You can see how some might find that explanation eerily similar to creation arguments about why god designed things this way or that way, don't you?

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Going back to the weather analogy, we know how storms are caused in principle. There is a mechanism that is known. The same is true in evolution. The mechanisms of mutation, selection, and speciation will cause bio-diversity in the same way that differential temperatures and pressures will cause storms. For the GodDidIt theories there is no mechanism that can be tested.

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Even with our limited knowledge of climatology we have enough data to make predictions that bear out. I think it is reasonable to expect us to come up with reasonable parameters about how long it SHOULD take to achieve speciation.

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In climatology we can make predictions, but they aren't that specific. For instance, no one can predict the temperature in NY city for December 21, 2015. Does that mean that we don't understand the mechanisms of climatology? Of course not. What SHOULD the temperature be on December 21, 2015? At best, between -100 and 100 degrees F. For speciation, we can come up with reasonable parameters but they will be as vague as weather predictions. In the short term, we can look at ring species and make very strong predictions on future speciation. We look at a stable ecological system and we can't make one simple prediction WRT speciation. We can predict that speciation will occur swiftly on an island that was previously barren. We can predict that speciation will occur less often in a stable ecology. I don't think we can make a simple "this many generations, this many species" prediction.

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I'm getting sick of that map phrase (no offense - but I swear I've read it about fifty times in the last week or so), and ultimately it smacks of a bit of a cop out. Sometimes a simple "we just don't know" is the most honest and accurate answer. Platitudes are rarely satisfying - how many religious platitudes do evos find solace in?

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I have read it quite a few times as well. Perhaps we should shrink it down to TMINTT to save space.I have always found the phrase to be instructive, a check on the reasoning behind a model. It reminds us that models should reflect reality, not the other way around. It is not a cop out. In fact it is quite the opposite. It a strong test of the logic behind the model.

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I read "the map is not the territory" and I hear "that's just the will of god" echoing in my head.

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I hear "all models are tentative and must adhere to reality". The voices in your head sound a lot more entertaining than mine do though.

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And that's what I'm looking for with are current knowledge of how evolution works - or how we THINK it works. How valid, or useful, is a theory that says "well a new species may or may not evolve in the next twenty thousand years." Crap, present that model to the Kansas School Board and ID will be part of the curriculum faster than boiled asparagus.

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Yeah, that's the problem with presenting science to lay people. They hear about what science can't do and figure that science must be wrong. I don't mean to disparage the lay public, but many people are surprised when they hear scientists express doubt.Speciation depends on factors that are random, chaotic, and independent of one another (eg mutations, climactic changes, volcanic eruptions, tidal waves). You would have a better chance of winning a lottery than predicting mutations in one individual in the next generation. Natural selection also pushes species in two directions, one force pushes species towards stability while the other force pushes towards change. To trot out another worn phrase, future speciation is being controlled by the Butterfly Effect. One small change early in the process could have large ramifications further down the pipeline.I think this is a very interesting thought experiment, don't get me wrong. I'll try to get off of this "wet blanket" tirade and see if I can't contribute something towards constructing a model.

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This makes me think that a variable (for a much grander model than what I'm futzing about with) would be some sort population plateau where the sheer number of an existing species would prevent continued evolution because any and all new mutations are eventually cycled back into the population at large; then the mutations are simply watered down and exist in isolated pockets, or just die out.

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Let's look at an ideal stable ecosystem and an ideal ecosystem moving towards stability.In an ideal stable ecosystem, all, or nearly all, of the available niches are filled by one species. Each species specializes in that niche and is so specialized that it can not survive outside of that niche. In this situation there will be no speciation (since we are dealing with an ideal situation). Natural selection will be pushing each species towards stability and away from change because every other possible "job" is already being done by another species and they are doing it better than your species could with just one generation of mutation. There are no ideal stable ecosystems, so this is a hypothetical situation. However, there are ecosystems that have been closestable for quite a long time and this is what we see.In an ideal developing ecosystem, you start with two species. One is a prey species and the other is a predator species. This could be an herbivore/plant relationship or a carnivore/prey relationship. In this situation there are a lot of possibilities for change. There are empty niches all over the place. Plants will grow larger to prevent over grazing while other plants will grow smaller so that the fit into little cracks to avoid grazing. Prey species will either grow larger or get faster. I think you get the idea.So in your model you also have to calculate the relative stability of the ecosystem. You could hypothetically calculate the maximum rate of speciation which would be tied in with the mutation rate and using the model of an initial two species ecosystem.

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Once the species reaches a certain level, it would become extremely resistant to additional speciation because the baseline genes (for lack of a better phrase) would keep the overall species characteristics near the mean.

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The phrase that is often used is "fitness peak". This is an analogy that works quite well for this discussion.Think of adaption as an uphill walk towards a peak which represents specialization. Each niche is then a peak with valleys between each of the niches. For a species to move into another niche it must go "downhill" (become less specialized), cross the valley, and then climb the next fitness peak. What happens in stable ecosystems is that the valleys become extremely deep. So deep that species are not able to make the traverse to the next peak. In a developing ecosystem the species are not very far up their fitness peaks. They are in the valleys and each path up each peak is a path of speciation.You must also remember that the mutation rate is the same for every species regardless of the stability of the ecosystem. In a stable ecosystem, beneficial mutations are rare because the species are all well adapted. Therefore, neutral mutations will be selected for in a stable ecosystem. In a developing ecosystem there are many possible beneficial mutations most of which will be selected for.

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think this would be a sort of punctuated equilibrium argument, no?

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Yeah, in a general sense. You will observe stasis in a stable ecosystem and punctuated evolution in developing ecosystems.

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So Joe Lowspermcount is a separate species from homo sapiens because he is unable to reproduce? Are you really saying that?

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Joe Lowspermcount may in fact be a new species. Ma and Pa Lowspermcount could also be separate species. However, individuals do not a species make. Species are a group of interbreeding individuals. One person is not an interbreeding group. Just as a wild, off the cuff, example: If the offspring from a Californian and a New Yorker always has low sperm count then we could consider this as the start of a speciation event. (For the moment ignore immigrations and all that).