All species are transitional

I'm talking about a successful species. Take our 50 creatures in the woods. Doesn't it begin with one? I think it unlikely that 2 creatures would be born, due to mutation, with some speckles. Over time the speckled creatures mated and produced a heavily speckled creature. At this point, a new species was produced because it could not recognize a non-speckled creature as a mate. The new species occurred when the heavily-speckled creature was produced. If one had a time machine, one could date it to a certain day, given the definition of species adopted by some---"gene pool isolation."However, if one adopts the definition of morphological change, then one can name one's new species whenever one likes.

But the heavy speakles are only isolated from the no speakles not from the lightly speakled which are not isloated from the no speakles.There is, therefore, some gene flow from heavy to no.

And your point, Nosy?

Well, not exactly. I mean, in our scenario, the skeletal remains off all three types of creatures would be identicle.We'd have to actually see a morph change in order to decide there was a new species.As such, it's much more likely that we've clumped multiple genetically seperate species together into single morphological groups - however if that's true, it only strengthens the case for speciation, in that ToE supporters are handicaping their own data

The point is that it isn't clear there is a really new species on the day of the first heavy. It is still not completely isolated from the gene pool. There is, in fact, still one gene pool.After that it could go on as one species with the no speakles dying out slowly or the mix of heavy, no and light continuing in the gene pool or split if something finally stops the heavies from breeding with anyone else.

What does this mean? We are trying to settle on a defintion of "species."--------------------------------------------------------------------------------

Ok, I understand. But there would come a point--would there not?--a quite definite day, when one had a new species (according to the definition). If one had a time machine, one could date it.

If you say this on the grounds that the heavily speckled creature doesn't recognize a non-speckled creature as a mate, then it is not the case that one species gave birth to another species, because you didn't say that the heavily speckled creature was born from a non-speckled creature.I presume the mother was only a teensy-weensy less heavily speckled than her offspring. Effectively they are the same species. But the heavily speckled creature and the non-speckled one it refuses to mate with are much further apart in the gene pool, and thus could be called different species.This message has been edited by Parasomnium, 27-Oct-2005 08:37 AM

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"We are all atheists about most of the gods that humanity has ever believed in. Some of us just go one god further." - Richard Dawkins

Yes, but the new species is only "new" with respect to specific creatures further distant in the gene pool. As I pointed out in my opening post, locally you cannot draw the line. A creature is the same species as its parents and its offspring, they're all too close together in the gene pool to make a difference. So, you can never say: "today, a creature of one species gave birth to a creature of another species".Also consider this: if you look at a certain creature, its "newness" - in terms of species - is not determined by this individual creature itself, but by its distance to the cousin you compare it with. If, on the basis of that comparison, you decide that it is not a new species, you only have to compare it with an even further distant cousin to be forced to conclude that you are dealing with a different species. Of course the creature hasn't changed, but your comparison has.If you put grains of sand together, one by one, at what precise moment do you start calling it a heap? Forget that there is a clear local boundary, there is only gradualness.This message has been edited by Parasomnium, 27-Oct-2005 10:29 AM

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"We are all atheists about most of the gods that humanity has ever believed in. Some of us just go one god further." - Richard Dawkins

Lets look at it this wayWe have 4 groups based on genetic possibilitiesNN - non-speckled (both genes)
SS - darkly speckled (both genes)
NS - lightly speckled (one gene each)
SN - lightly speckled (one gene each)for all intents and purposes NS = SN so we can reduce this to 3 groupsNow assume thatNN mates with NN or NS but not SS
NS mates with NN or NS or SS
SS mates with SS or NS but not NNWe have isolation between NN and SS but not anywhere else in the population, so there is still some interbreeding between all others and still some genetic interchange between NN and SS by way of NS interactions.Note that NS is as large as both NN and SS combined, once S has become established in the population (which started as NN) AND in the absence of selection pressure to diverge.Is this a new species on day one of SS? Not really, because still breeds with a major (NS) portion of the population that is still part of the "old" species. It rather the beginning of the divergence.Final divergence is achieved when NS disappears due to sexual selection of NN for only NN {AND?\OR?} of SS for only SS.

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Well, like I said, there are multiple definitions. Some fit better than others given circumstances.In your scenario, a morphological definition is not sufficient.
In the fossil record, an interbreeding scenario is not sufficient.I think an interbreeding definition of species is a "Better" definition, since it can seperate individuals which other catagories would group together.However, interbreeding requires multiple living representatives in order to be tested, therefore can not be used to examine the fossil record, for example.

Let me go over this and see if I can clarify it in my own mind.Let me add a little to the scenario by saying that the speckled coat is important for survival, and the MORE HEAVILY SPECKLED it is the better. There are some big bad predators around, and the only way these little critters can defend themselves is by hiding. The heavy speckles allow them to blend visuallly into the bushes. They happen to be Eutherians--ancestors of me and my cat--and if this little group doesn't survive I and my cat won't ever exist. We need more speckles!The initial light speckles was created by a mutation.What I'm trying to figure out now is how the coat goes from slightly to heavily speckled. Surely there is not a series of mutations as regards just this one feature (the presence of speckles). That would seem very unlikely, unless I'm confused about the nature of mutations.I was thinking that when you got to the point, after some generations pass, that two lightly speckled critters mated, this might produce within the litters some heavily speckled ones. When a dog has puppies, you get all sorts of patterns on the coats. So I think that's plausible. I suppose imperfect replication is enough to keep the trend going toward the heavily speckled? The environmental "pressure" is such that the lightly speckled creatures are more likely to reproduce but that doesn't mean the trait (heavy speckles) is just going to show up. It shows up by chance.As regards the issue of speciation, I'll address that in another post.Here I'm just wondering about the mechanism from lightly to heavily speckled.This message has been edited by robinrohan, 10-27-2005 01:11 PM

Hi robin,I agree that it seems unlikely that there are whole bunch of genes that control the amount of speckling on an animal's coat. But that isn't really the way that the speckling is being specified. The amount of speckling will likely be determined by some threshold mechanism that operates during development; Perhaps there is a hormone or something that causes pigmentation to develop when it reaches a local threshold, and this hormone is in a feedback loop with an inhibitor such that if one part of the skin is high in concentration of the hormone, it's neighbours will be low. Slight changes to the threshold level of the hormone's activity and slight changes to the decay rate, the feedback mechanism, etc. might well produce a huge variety of different specklinesses, from spots to stripes, dots, cheetah spots, etc. etc.This has been anlysed by simulation using cellular automata, see here and hereThese models are a bit more elegant and a bit more parsimonious than the straightforward gene->phenotype kind of thing you're thinking of. You know, there is not one gene per speckle or anything like that Mick

Even if it isn't all that likely it depends on more details of the scenario. But it would be demonstrating a different point.I'd say that the mix of no, heavy and light speckles (I think I finally have the spelling right) isn't so likely. Rather we would get some speckling become the only coat in the population over time. Then some other mutation happens that increases it a bit more. This too becomes "fixed" (all through the population). This carries on over time. However unlikely the chain of mutations is they can arise if the population isn't too small and we allow enough generations.This isn't what we have been discussing because we were showing the "fuzziness" of speciation. The above scenario still does but it is now spread out over time so it isn't so apparent.It is, just to muddy things a bit more, entirely possible that all 3 forms of no, heavy and light speckling will stay in the population. This could occur if the environment consisted of some bush and some open savana kind of places (think lion colored coat with no marks). If one coat offered a level of advantage in part of the environment and one in another they may all be preserved in the population.In that case, over time, the no speckle form may occupy the open areas and the heavy speckles the bush and we would see the speciation without losing either one. If the climate changed back and forth we could see the population tracking it a bit too.It maybe that homo ancestors went through something like this if being aboreal was of greater and lessor advantage and moved back and forth as the climate changed.

I don't understand how you could. It's self-evident to me that gene flow exists between a parent and its offspring; thus, no reproductive isolation.