Genetics and Evolutionary Experiments

This article in the Washington Post helps counteract an false assumption about evolution that many have made. This is the assumption that because evolution is a theory of historical change it can only be confirmed by the fossil record, rather than by performing experiments today that make potentially confirmable or falsifiable predictions. In fact that's not the case:

When scientists announced last month they had determined the exact order of all 3 billion bits of genetic code that go into making a chimpanzee, it was no surprise that the sequence was more than 96 percent identical to the human genome. Charles Darwin had deduced more than a century ago that chimps were among humans' closest cousins.

But decoding chimpanzees' DNA allowed scientists to do more than just refine their estimates of how similar humans and chimps are. It let them put the very theory of evolution to some tough new tests.

If Darwin was right, for example, then scientists should be able to perform a neat trick. Using a mathematical formula that emerges from evolutionary theory, they should be able to predict the number of harmful mutations in chimpanzee DNA by knowing the number of mutations in a different species' DNA and the two animals' population sizes.

"That's a very specific prediction," said Eric Lander, a geneticist at the Broad Institute of MIT and Harvard in Cambridge, Mass., and a leader in the chimp project.

Sure enough, when Lander and his colleagues tallied the harmful mutations in the chimp genome, the number fit perfectly into the range that evolutionary theory had predicted.

Their analysis was just the latest of many in such disparate fields as genetics, biochemistry, geology and paleontology that in recent years have added new credence to the central tenet of evolutionary theory: That a smidgeon of cells 3.5 billion years ago could -- through mechanisms no more extraordinary than random mutation and natural selection -- give rise to the astonishing tapestry of biological diversity that today thrives on Earth.

Evolution's repeated power to predict the unexpected goes a long way toward explaining why so many scientists and others are practically apoplectic over the recent decision by a Pennsylvania school board to treat evolution as an unproven hypothesis, on par with "alternative" explanations such as Intelligent Design (ID), the proposition that life as we know it could not have arisen without the helping hand of some mysterious intelligent force.

Contemporary genetics is now strongly computational, involving the manipulation of databases. As genetics has become digitized, it has become possible to perform experiments that can confirm or disconfirm particular theories of evolutionary development, and indeed, the basic claims of evolution itself. So far, Darwin's basic claims have held up remarkably well, indeed as well as probably any other scientific theory first proposed in the middle of the 19th century.