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The Part That Natural Selection Plays

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Posted by Michael W. Pearson on September 13, 2002 09:58:23 UTC

Sam asked:
" Did little finchs start beating their brains out
for no reason long enough to evolve very sophisticated beaks and tongues?"

Hi Sam
Here's how natural selection would work in this situation:
Birds which are the approximate size of finches and woodpeckers were, a million years ago, already finding their bug food in the bark and outer layers of trees. If we assume that for some time, no birds behaved as woodpeckers do -- pecking holes to get at inner layers -- then here is a way that natural selection would form birds that do, while still leaving birds that do not do that:
1) Some birds have longer beaks than others.
Some birds might also develop a strange tendency to jerk forward. In fact, many such nervous system quirks could have been coded in the DNA, but most of them would not help a bird, and those birds would be unlikely to live to reproduce in the natural world. There is no selection involved...only lack of advantage.
We saw in the previous post that this rise of new traits, including nervous system quirks and
longer beaks, could occur
with a chance mutation, a change, in the DNA code which is conveyed to a new individual in the sperm and egg of the parent birds.
When the
food supply in trees ran low, there would be an advantage for tree-feeding birds who could dig DEEPER into the bark to get burrowing insects and other bugs. More of the deeper digging ones might live to procreate one or more years than birds who experienced famine in bad periods because of a shortage of bug food.
Over a thousand generations, this could mean the birds with stronger neck muscles and longer beaks would become more numerous than the first wave of them that appeared.

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