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Sunday, January 27, 2008

Design of Life: Extinction - and so, good night, the final curtain ...

Textbooks often don't discuss extinction - the death of all members of a species - in any detail. No surprise there, it's a frustrating and depressing topic.

Frustrating because museums would bid billions to bring back a live tyrannosaur. And depressing because good answers are often not available. So discussion can lurch dangerously into the realm of folklore.

When that happens, folklore wins hands down over fact. The extinction of the entire superorder of dinosaurs [1] which marked the close of the Cretaceous era - perhaps mainly due to an asteroid hit - has become a pop culture icon that now supports a variety of views and causes.

Pop culture need not - and does not - address the real history of life. For example, the extinction of all species of trilobite, the signature fossil of the Cambrian era, goes largely unnoticed simply because trilobites never became a pop culture icon. In any event, when discussing extinctions, competent and honest scientists can reach different conclusions. [2] But understanding the history of life requires that we grapple with what we do know about natural* extinctions, as well as about the actual patterns of evolution and of stasis (vast periods in which nothing much happens to a life form).

[ ... ]

Raup ends his 1991 book on a curious note, attributing to Darwin's theory of evolution powers he does not actually discuss in his own book - yet he then reserves a key judgment:

“Is extinction through bad luck a challenge to Darwin’s natural selection? No. Natural selection remains the only viable, naturalistic explanation we have for sophisticated adaptations like eyes and wings. We would not be here without natural selection. Extinction by bad luck merely adds another element to the evolutionary process, operating at the level species, families, and classes, rather than the level of local breeding populations of single species. Thus, Darwinism is alive and well, but, I submit, it cannot have operated by itself to produce the diversity of life today.”

- David M. Raup, Extinction: Bad Genes or Bad Luck? (New York: W.W. Norton & Company, 1991), p. 192.

Interesting! What does he think "Darwin's natural selection" cannot have done? Compare this with what he says in the quotation just above, about the Pleistocene rain forests.

In his day, Raup was taking a big risk by even suggesting that Darwinism might not be true, so he wisely merely provides facts that dispute it - and then covers his tracks with a resounding promotion of Darwinism in areas of study that he does not actually address in his book.

Sometimes, that is the only way to get key information across.

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