Art of the taxidermist and expertise of the scientist-curator combine to suggest the variety of life-forms to which evolution has given rise in the animal kingdom alone. The exhibit was photographed in the Hall of Biodiversity at the American Museum of Natural History in New York City.
Grant Delin

Key Concepts

• Charles Darwin’s theory that evolution is driven by natural selection—by inherited changes that enhance survival—struggled against competing theories for the acceptance it has within biology today.
• Random genetic mutations having neither positive nor negative effects were once thought to drive most changes at the molecular level. But recent experiments show that natural selection of beneficial genetic mutations is quite common.
• Studies in plant genetics show that changes in a single gene sometimes have a large effect on adaptive differences between species.

Some ideas are discovered late in the history of a scientific discipline because they are subtle, complex or otherwise difficult. Natural selection was not one of these. Although compared with other revolutionary scientific ideas it was discovered fairly recently—Charles Darwin and Alfred Russel Wallace wrote on the subject in 1858, and Darwin’s On the Origin of Species appeared in 1859—the idea of natural selection is simplicity itself. Some kinds of organisms survive better in certain conditions than others do; such organisms leave more progeny and so become more common with time. The environment thus “selects” those organisms best adapted to present conditions. If environmental conditions change, organisms that happen to possess the most adaptive characteristics for those new conditions will come to predominate. Darwinism was revolutionary not because it made arcane claims about biology but because it suggested that nature’s underlying logic might be surprisingly simple.

In spite of this simplicity, the theory of natural selection has suffered a long and tortuous history. Darwin’s claim that species evolve was rapidly accepted by biologists, but his separate claim that natural selection drives most of the change was not. Indeed, natural selection was not accepted as a key evolutionary force until well into the 20th century.

   
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