ok, so If i have a baby which survives, thats natural selection taking place???
Yes. Keeping in mind that by
survive, we don't just mean, lives long enough to be buried instead of being used as an ingredient in shampoo. We mean, lives long enough to have babies of her own. Got it?
Now, if you have a baby with one big eye in the middle of her forehead, that's
mutation. This is true even if she becomes hair product. See the difference?
Good. So, if you have a baby born with one big eye in the middle of her forehead, who lives long enough to have babies of her own, some of whom either have, or have children who have, one big eye in the middle of their forehead, then that would be
evolution.
But if you also have perfectly normal babies, and they have perfectly normal babies, that's still selection. And if they keep at it, generation after generation, and eventually the whole township looks a lot like you and no one at all looks like your ugly neighbors, that's still evolution.
And if a big polar bear comes along one day, and starts eating every one up, and is doing fine until he gets to your house, and the one-big-eye people come out, and it totally freaks him out and he runs away, then that's
natural selection driven by mutation.
So if the one-big-eye people decide the non-bear-scaring regular descendants are inferior, and make a practice of not breeding with them, that's
speciation. When occasionally some perverse couple do it anyway, that's
hybridization. If mutations or other gene incompatibilies pile up to the point where the two groups stop being able to have babies together at all, even if they wanted to, that would be
macro-evolution.
However, if it were just the blondes and brunettes who decided as a rule not to interbreed, that would still be speciation. And if, as a result of the excessive inbreeding involved in a practice like this, a hemophilia gene piled up on one side and a tendency toward lesions piled up on the other, so that whenever someone tried to break the rules and crossbreed, their embryos just immediately bled to death before they could even become placentique; that would still be macro-evolution.
Yeah, that
does imply that at one time under some conditions blacks and whites could be considered separate species (falsely, as interbreeding did continue, the offspring were just assigned by fiat to one group rather than the other, but let it pass for this example) and that now, on the other hand, they couldn't. That would be an interesting example of
genetic drift.
Note that at no point in this story does natural selection change anybody's traits. All it does is fail to kill some of them before they can spawn. The new traits come in the form of freaks and immigrants and inbreds. Natural selection doesn't care, it wants to kill them all. The freak immigrant inbreds might be the ones who dodge better, or the normal native mulattos. It doesn't care, it doesn't even know the difference, it just keeps spraying its house with different concoctions and complaining that nothing seems to quite take the vermin out completely.
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