From: John Beckett 

Adam  wrote in message
news::
> But why should be being chased by cheetahs make the pronghorn antelope fast?

Is this a trick question, or is there some faint chance that you are
seriously asking?

Being chased by cheetahs does not make anything faster. However, any tiny,
random mutations which cause antelopes to run faster will be rewarded in
future generations, and those mutations will become more prevalent.

Also, cheetahs will never run MUCH faster than their fastest prey. Because
the effort their bodies spend on being able to go faster than necessary
would mean that other cheetahs, whose genes didn't bother with the excess
speed, would be able to develop in other ways (e.g. give birth to more
young) that would multiply the "slow" genes.

I might even tell you about pronking antelopes, but I'm still puzzled about
what line you are pursuing.

John

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