What would Lamarck have said about a woodpecker's cushioned head? And how would Darwin have replied? A hypothetical conversation:
Lamarck: Bonjour Charles!
Darwin: Cheerio Jean-Baptiste!
Lamarck: Ze woodpecker is a hard-headed old fellow no?
Darwin: Yes, thanks to natural selection.
Lamarck: Aah mon ami (shaking head dubiously). I say it is due to using his head over and over again to make holes in ze trees! He uses it and uses it and develops a cushioning layer from all this use. That cushion protects him. His little baby woodpecker inherits it from him no?
Darwin: Jean-Baptiste, you have made a mistake. The woodpecker inherits the cushioned head as follows:
Imagine a large population of woodpeckers. Some have well-cushioned heads, some have less-cushioned heads.
Woodpeckers with well-cushioned heads can peck holes in trees more effectively than woodpeckers with less-cushioned heads. This enabled the woodpeckers with well-cushioned heads to survive better during times of low food supply than their less-cushioned counterparts.
The woodpeckers with well-cushioned heads have a trait that helps them survive longer. This makes them more attractive to female woodpeckers. And as a result, they reproduce more.
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