All species are transitional

Wonderful!

That was the general idea, yes.---A while back you said: I answered: "That isn't going to work."Then you said: Could you expand on that a bit? I'm not too happy with approaching the subject "politically", but maybe you can change my mind.This message has been edited by Parasomnium, 25-Oct-2005 08:48 PM

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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

If you wanted to explain the problem of someone thinking in terms of "kinds"--which is a "natural" way to think--it's much easier to explain it to them by defining "species" in terms of changes in the body of a life form rather than "gene pool isolation."Let's think about fossils. Now here all we have are snapshots of what a life form looks like. There is no data about gene pool isolation, I assume, except in some rare case. Say we had 40 fossils along an evolutionary branch. Fossil #1 is the oldest and fossil #40 the most recent. They all look a little different. It's easy for someone to realize that we could label fossil #24 or #25 or #26 as a new species if we wanted to or, if we wanted to, we could call them all different species. This shows us that "macroevolution" is a meaningless term.So by "political," I mean pedagogical, with the understanding that this whole issue has political implications. Sometimes a teacher has to simplify.The layman (such as myself) tends to think in terms of fossils when he considers the evidence for TOE.It's less easy--as it was less easy for me--to visualize the point of "gene pool isolation" as something gradual and, above all, as something arbitrary. In fact, "arbitrary" seems to be the wrong word in this context, but it seems just the right word using the other definition.This message has been edited by robinrohan, 10-25-2005 02:48 PM

I see a problem here. When the fossils are morphologically too close together, the creationist will say that the changes between #24, #25 and #26 are due to natural variation within one species. And when the fossils are too far apart, the creationist will say that they are different species and demand to be shown a transitional.Besides, is your sequence of fourty fossils not just a coarser example of the gradual model? I think that only when we take each and every intermediate into account - that is, a seamless row of ancestors, a theoretical possibility only - the creationist can no longer reasonably demand yet more intermediates. Then it's high time that was changed. We need new thinking tools, and better education, and the realisation that science offers so much more in evidence from other fields. Fossils are almost just illustrations to the story other evidence tells us. Did the graphic help, and if so, in what way?

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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

I think is much easier to understand that a decision between "natural variation" and "different species" is a mere matter of labelling. It has the advantage of not being an analogy. This other evidence is vague to most people. Something about DNA.The graphic showed me the gradual nature of gene pool isolation. I'm still a little shaky about it but I grasped it well enough, I think. Here's the way I understand it: You've got group A (wolves) and later on you've got two other groups (dane and chihuahua). During this period of change some of the proto-danes and some of the proto-chihuahuas continued to interbreed and some couldn't. Eventually it got to the point where none of them could. If we are speaking of individuals, either you can interbreed or you can't. If we are speaking of the entire group, then we can speak of a gradual process of isolation and therefore of "semi-isolation." That's the "intermediate" that I was looking for.This message has been edited by robinrohan, 10-25-2005 04:21 PM

Here's the problem: I was thinking that "arbitrary" meant we might say that a variation is a new species or we might not. It's just a label. But gene pool isolation is not arbitrary. We can't say that we can call two groups isolated, or maybe we can call them non-isolated.They either are isolated or they are not. We can say that some of the group are isolated and some not, and call that semi-isolation, and thus gradualness of isolation can be seen to take place. But whenever all of them are isolated, then we are not applying an arbitrary label by calling them a different species.This message has been edited by robinrohan, 10-25-2005 04:37 PM

There's a group of 50 black furry creatures living in the woods. One day, one of these creatures gives birth to one that has some yellowish speckles on its coat. It turns out that this slightly speckled coat has the effect of camouflage in the bushes. This speckled creature thrives and mates with an un-speckled creature. Several of the litter are speckled. They also thrive and mate. Eventually through some more generations, a speckled creature mates with another speckled creature, and the result is offspring that are even more speckled. When this heavily speckled creatue meets an un-speckled creature, they do not recognize each other as potential mates. So this heavily speckled creature must mate with another speckled creature. This trend continues.Is there a particular point in time, a particular generation, which we can say is a new species, using the definition of isolated gene pool?Generation #1--one slightly speckled creature
Generation #2--3 slightly speckled out of a litter of 6
#3--5 slight spleckled
#10--20 slightly speckled
#11--2 heavily speckled
#18--15 heavily speckledThis message has been edited by robinrohan, 10-26-2005 01:27 PM

You already included it: That is isolation by sexual selection, failure to mix genes.Where the gray fuzzy boundary lies is when the intermediately speckled still mate with both the unspeckled and the heavily speckled. This can still lead to some genetic flow between the two isolated populations but it is generations apart (carried by the lightly speckled ones)

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So it's valid to say that that first heavily speckled creature--the first one ever--is a new species when he is born?ABE: that would be one species giving birth to another species.This message has been edited by robinrohan, 10-26-2005 08:17 PM

I think you're going to find it's a lot harder to draw the line than you'd like it to be.By analogy - one drop of water is not rain. Ten drops of water, not rain. An inch in an hour - that's definately rain. So when did it start raining? There's no clear line to be drawn; you could say "after 1000 drops" but it's not really raining any less at 999 drops, or any more at 1001 drops.You can tell when its raining. You can tell when its not raining. But any line you draw between "raining" and "not raining" is going to be arbitrary, because, contrary to the black-and-white nature of the way we've constructed language to describe the weather, there's a continumm between raining and not-raining.Another way to look at it is probabilistically. At "not-raining", there's a 0% chance that you would be correct to say it was raining. At "raining", there's a 100% chance that you would be correct to say so. Somewhere in between there was a 50% chance that it was raining at that point in time, but there's no way to know 100% if it was raining or not. At that point, your confidence in your statement that it is raining is only 50%.So too with species. Sorry if the analogy was tortuous.

It's not about "liking it to be," old buddy--it's about figuring it out. And I am determined, in my simple-minded way, to figure it out. Your rain analogy was pretty good.But what I want to know is--if one could go back in time--if one could identify a particular species being born from another species at a particular time.The way I figure it is, it depends on what definition of "species" one adopts. Now this is all very difficult. What I want it to be is arbitrary. We could call the heavily-speckled creatures a different species if we wanted to, but we could also call them a variant. However, if we adopt the definition suggested by Parasomnium, I'm not sure we could call them a variant.

You're right that it is difficult. Since there are multiple definitions of species, and many of them are not testable against, lets say, the fossil record, it's hard to pick one as being better than the others.I think Para's definition is a good one. In this case, the fully speckled one could be a seperate species - BUT...If only 1 of these super-speckled offspring is born, then they do not form a seperate population. We'd me more likely to classify the single offspring as a freak.Part of the problem is in the scenario. The changes you suggest are clear and easy to understand, but are also much more rapid than they would happen in the wild.An example I like to sight is jumping spiders. There are species of jumping spiders which look identicle, which have virtually identicle genetics, but which have slightly different mating dances. As a result a member of group 1 can not mate with a member of group 2.Now, it's unlikely that the mating dance 1 became mating dance 2 in one or two steps, since the one step would make the performer unmatable.But a tiny difference here, a tiny difference there. Enough to be different, but still get the point across. 6-7 of these small changes over a few decades and you've got a completely different species.

But doesn't it begin with one?

Gray area. If 1 is born and only 1 ever lives, was that 1 a new species? A rain storm begins with 1 drop, but at the moment that drop falls, you can't say - this is the beginning of rain. All you can say is "oh look, a rain drop"

Remember the speakled beasties are a contrived example. There will be many more gradiations of larger and larger speckles in most real examples.