Tuesday, November 24, 2009

Happy Anniversary

One hundred fifty years ago today, the first edition of Charles Darwin's masterpiece On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life was published.

I picked up a copy of the book a few years ago for about $10, when the American Museum of Natural History in Manhattan had a Darwin exhibit. The most memorable display for me was the handwritten notebook entry where he first speculated about the tree-like connectivity between different species. I was humbled to be within a few feet of this tangible record of his world-changing inspiration, written with his own pen.

The book itself was very readable, intended as it was for an audience far beyond specialists. Starting with what would then have been familiar techniques of plant and animal breeding--"artificial selection"-- Darwin proposes conceptually extending that process to nature. Combining natural variation with its heritability, a Malthusian appreciation of the struggle to survive and an awareness of the immensity of geographic time, this extension seems eminently reasonable.

And yet there are challenges. Rather than bluster through them, Darwin addresses them head on, conveying an honesty and openmindededness that is bracingly refreshing in our argumentative times.

He confronted head-on, for example, the intellectual challenges of the intricate structure of the eye, fully admitting that the theory demanded that at every step of evolution there be some function for the intermediate forms. Even today, intelligent design proponents profess to be flummoxed by the very challenges that Darwin faced--and faced down.

Darwin also clearly described the tradeoffs needed for the evolution of traits like altruism, avoiding the temptation to invoke the "good of the species." To persist, such traits must provide an advantage to the group that exceeds the cost to individuals. This clear statement of the constraints of group selection needs wider appreciation today.

In these and many other areas, Darwin anticipated and addressed the confusing aspects of his explanation for evolution. And he did it all without even the benefit of Mendel's laws of genetics.

Time and again in the intervening decades, newly uncovered evidence from biology and paleontology has reinforced the essential correctness of Darwin's framework. The laws of genetics and of their DNA mechanism, the fossil record of transitional forms, and mathematical models have all confirmed and clarified the power of undirected selection of random variation for driving innovative new possibilities.

There are caveats, of course. Non-inherited mechanisms of genetic transfer change the story in important ways, especially near the single-celled trunk of the tree of life. Such revisions are hardly surprising after 150 years of scientific advancement.

What is humbling is the persistent soundness of the essence of Darwin's vision, and of this amazing book.

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