By Steve Mirsky
“If I were to give an award for the single best idea anyone ever had, I’d give it to Darwin.” So wrote philosopher Daniel Dennett in his 1995 book Darwin’s Dangerous Idea. “In a single stroke, the idea of evolution by natural selection unifies the realm of life, meaning and purpose with the realm of space and time, cause and effect, mechanism and physical law.”
Dennett’s musing really hits home to anyone who took introductory biology that did not include evolution: such a course is a giant survey of the different kinds of plants, animals and other organisms of our planet, tied together by a single principle–you needed to know it for the final. But evolution by natural selection ties all life together with process and chemistry. As the great biologist Theodosius Dobzhansky famously, and correctly, said, “Nothing in biology makes sense except in the light of evolution.”
The idea itself is fairly easy to grasp (which may be one reason why people who would never dream of finding fault with Einstein feel qualified to dispute Darwin): in populations of organisms, each individual is a bit different from every other; the differences may give that individual a bit of a survival advantage; that individual is more likely to pass on the traits that helped it survive; that trait becomes more widespread; rinse; repeat. In a few hundred million years, you can go from amoebae to elephants (and still have amoebae).
Of course, in the decades since the publication of Origin of Species, scientists have learned much more about the evolutionary process than Darwin could have dreamed of. Genes get duplicated; chromosomes get rearranged; viruses shuttle genetic information from one species directly to another; individual genes govern the activity of other genes. But Darwin got much of the overall picture right–a remarkable achievement for a man working with whole organisms, before the unraveling of heredity on the molecular level of DNA.
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