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The
Atheist Devotional: Timeless Meditations for
the Godless by M. Moore
Copyright ă 2008 M.
-Reading Number Fifteen -
Another Yarn from Dawkins
Excerpted from: Dawkins, The Blind Watchmaker, Chapter 9*
Hey, boys and girls! It’s story time once more. This one’s about shrews.
“...Here, then, is our orthodox neo-Darwinian picture of how a typical species is 'born'... We start with the ancestral species...spread over a large land mass. They could be any sort of animal, but let's carry on thinking of shrews. The landmass is cut in two by a mountain range. This is hostile country and the shrews are unlikely to cross it, but it is not quite impossible and very occasionally one or two do end up in the lowlands on the other side. Here they can flourish, and they give rise to an outlying population of the species, effectively cut off from the main population. Now the two populations breed and breed separately, mixing their genes on each side of the mountains but not across the mountains. As time goes by, any changes in the genetic composition of one population are spread by breeding throughout that population but not across to the other population...So the two populations diverge genetically: they become progressively more unlike each other. “They become so unlike each other that, after a while, naturalists would see them as belonging to different 'races'. After a longer time, they will have diverged so far that we should classify them as different species. Now imagine that the climate warms up so that travel through the mountain passes becomes easier and some of the new species start trickling back to their ancestral homelands. When they meet the descendants of their long-lost cousins, it turns out that they have diverged so far in their genetic makeup that they can no longer successfully interbreed with them...'Speciation' is complete. We now have two species where previously there was one, and the two species can coexist in the same area without interbreeding with one another. Actually, the likelihood is that the two species would not coexist for very long...because they would compete. ...[I]f there is significant competition between the two species, most ecologists would expect one or other species to go extinct in the area of overlap. If it happened to be the original, ancestral species that was driven extinct, we should say that it had been replaced by the new, immigrant species.
Good story, huh? So good it just has to be true! It’s too compelling to the imagination not to be...even though there are a lot of things that have to happen in just the right way, or the whole plan fails: 1) There has to be a barrier (the mountain range) separating the shrews from an area with no shrews, a barrier that is almost impossible for the shrews to cross, but 2) it is not quite impossible for them to cross. 3) “One or two” shrews do cross it. Now I wonder, how would that work if it’s just one? Well, it would have to be a pregnant female, for obvious reasons (we all know that pregnant females just love to venture out and cross dangerous mountain ranges); if it’s two, it could be a male and female out on a joint venture. 4) After surviving the mountain crossing, those one or two shrews and their progeny survive long enough to start a new population (the plan obviously fails if the shrew makes it all the way across the mountains only to be immediately eaten by a snake), and that population is successful and flourishes. 5) The new population experiences mutations and selection that make it evolve into something else. 6) The climate warms up and makes the mountains passable—but only after a sufficiently long time has passed for the two populations to have diverged into two new species that can’t interbreed. 7) For some reason the two new species are forced to now compete on the same territory instead of each staying in separate territories. 8) There is “significant” enough competition to drive one species extinct. 9) The ancestral species is the one that is driven extinct (even though Dawkins has them fighting on their own territory with a new species that evolved in order to adapt to some other environment). If all these things happen in just the right coordinated way, then—voila!—evolution has made one tiny step forward. The ancestral species is gone, and the new version is ready to repeat the whole process to make the next tiny step in evolution.
The theory of speciation resulting from initial geographical separation has long been a cornerstone of mainstream, orthodox nee-Darwinism, and it is still accepted on all sides as the main process by which new species come into existence (some people think there are others as well).
So most of the millions and millions of species that have ever existed on Earth arose by means of this kind of detailed, coordinated process. Just by chance all the necessary steps came about in just the right way, and (also just by chance) it happened over and over, millions of times—once for each of the millions of speciations that had to have happened if the theory of evolution is to be believed. Well, sure, I can swallow that. We don’t know for sure that it’s impossible. And as I said before, I can believe anything as long as it’s not impossible. Anything to avoid being one of those despicable creationists. Yuck. Creationists are even so thick-headed as to doubt that humans evolved from an amoeba:
...Incidentally, it is worth quoting J. B. S. Haldane's characteristic piece of lateral thinking in combating the same source of incredulity [about the idea that humans evolved from an amoeba]. Something like the transition from amoeba to man, he pointed out, goes on in every mother's womb in a mere nine months. Development is admittedly a very different process from evolution
Very different? Yeah, that would be an understatement. Last I heard there was no mutation and natural selection going on in the womb, no struggle for existence with survival of the fittest. And I’m pretty sure the fetus doesn’t engage in any arms races against predators or prey in there either. The fertilized egg is also different from that first cell that we evolutionists all believe by faith that we came from, in the slight detail that the first cell had no blueprints ready-made inside it for making a human being. All it knew how to make was another simple cell like itself. Also, the fact that one process takes nine months and the other took (we’re told) four billion years should clue us in to how different they are.
but, nevertheless, anyone sceptical of the very possibility of a transition from single cell to man has only to contemplate his own foetal beginnings to have his doubts allayed.
I have to admit, I find it hard to see how contemplating the transition from fertilized egg to fully-grown human assures us of the possibility of anything except...the transition from fertilized egg to fully-grown human. It’s like saying, “If you doubt the very possibility that that National Enquirer story about a woman giving birth to a rhinoceros could be true, just remember that humans and rhinos both start from a single, fertilized egg!” But maybe I’m just not good enough at “lateral thinking.”
* “Excerpts” are paraphrased, except for “words in quotation marks and italics,” which are direct quotations from the excerpted work.
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