john2072
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 Wysłany: Sob 14:36, 05 Mar 2011 Temat postu: On the Makaloa Mat LondonJack Publishedaambtf |
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ngest ears you'll succeed in increasing the average in
later generations. For a while. But if you continue to breed from those with
the longest ears there will come a time when the necessary variation is no
longer available. They'll all have the 'longest' earsand evolution will grind
to a halt. In normal evolution this sort of thing is not a problembecause
most environments don't carry on exerting consistent and unswerving
pressure in one direction. The 'best' length for any particular bit of an
animal will normally not be 'a bit longer than the present averagewhatever
the present average may be'. The best length is more likely to be a fixed
quantitysay three inches. But sexual selection really can have the embar-
rassing property of chasing an ever-driving 'optimum'. F [link widoczny dla zalogowanych][link widoczny dla zalogowanych]le fashion
really could desire ever longer male earsno matter how long the ears of the
current population might already be. So variation really could seriously run
out. And yet sexual selection does seem to have worked; we do see absurdly
exaggerated male ornaments. We seem to have a paradoxwhich we may call
the paradox of the vanishing variation.
Lande's solution to the paradox is mutation. There will always be enough
mutationhe thinksto fuel sustained selection. Tyilai:
[link widoczny dla zalogowanych]
[link widoczny dla zalogowanych]
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