I have a problem with the theory of evolution, which I was going to bring up in my last post, but I was revising for my exam I had this afternoon (it went quite well, thanks for asking), so I left it until today.
Yes I can hear all you creationists out there, “what’s that you say? A secular humanist doubting evolution? This is surely evidence that we were right all along!” Well screw you all, that’s not what I’m saying. Let me explain my problem.
The issue was brought up by Dr Marc Surtees of the Edinburgh Creation Group during a post-talk discussion. We’re all agreed that small changes through reproduction and mutation, combined with natural selection over a long period of time is why species are different from each other today. Now one difference between species is that they often have different numbers of chromosomes. My problem is how this comes about through mutation and natural selection.
So I’m sure you’re all aware of the similarity in chromosomes between chimps and humans, and that it appears that two of the chimp chromosomes at one point fused together to form one of the modern human chromosomes, I believe it’s the 2nd, but I could be mistaken so don’t quote me. Anyway someone brought up this remarkable similarity, and the fusion, as evidence that humans and chimps are related, but Dr Marc turned the conversation around and showed how this is one of the greatest arguments against evolution.
The way evolution works with mutation, means that at some point one individual human ancestor must have had a mutation which meant the 2 chromosomes that we still find in chimps fused into the one we now see in the modern human. You can’t have half a chromosome, so it must have happened in one stage. Now we have one individual with 23 chromosomes, and all the rest of his/her species has 24. How does s/he reproduce? You need the same number of chromosomes as your mate to produce fertile offspring. How does this mutation get passed on?
Now I was going to email some experts and ask them (if I can find Dawkins’ email on RDF I’ll probably ask him too, hehe), but it appears I’ve already found the answer. Once again it seems the creationist camp has been very short sighted again (either that or Dr Marc was lying, but it looks like other people have made the same mistake). The reason people think you need the same number of chromosomes to reproduce fertile offspring is because of the well known example that if you cross a horse with a donkey, you get a mule, which is infertile. Apparently this isn’t true across the board as creationists seem to think. This article says (a third down the page, paragraph starts “some may raise the objection”), that a Przewalski’s Wild Horse, the closest wild relative of the domesticated horse, has 66 chromosomes, in comparison with the 64 of the domesticated horse, but they can produce fertile offspring. I’d be interested in finding out more about the genetic make-up of the offspring though. So it’s not such a problem.
I think I’m still going to email around anyway, just in case there’s another explanation.
Listening to: Coheed and Cambria – Blood Red Summer