Are we somehow expecting to see evidence of chromosome change in the fossil record? Because that's the only thing I can at all see has not been explained here.
And if it is, here's the answer. DNA doesn't fossilize at all well.
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Gillian
"Now everyone was giving her that kind of look UFOlogists get when they suddenly say, 'Hey, if you shade your eyes you can see it is just a flock of geese after all.'"
"You can't erase icing."
"I can't believe it doesn't work! I found it on the internet, man!"