Balkinization: Genetics and Evolutionary Experiments

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.

Posted 2:56 PM by JB [link]

Comments:

This seems rather beside the point. No one disputes the role of natural selection in maintaining the stability of species and reducing the number of harmful mutations. The real issue is whether random variation and natural selection explain speciation. (That is why Darwin called his book "On the Origin of Species," not "On the Stability of Species.") The results in this article don't bear on the mechanism of speciation at all.

# posted by

sean : 3:44 PM

Sean: What do you mean by "the role of natural slection in...reducing the number of harmful mutations?" Selection occurs after mutation. Also, is your claim that a (the?) central tenet of intelligent design is "mutation plus isolation can't produce organisms who are capable of reproducing with members of the population which they are part of but incapable of mating with members of the other population." Because that's speciation.

# posted by

washerdreyer : 9:17 PM

In the cultural war of ID vs. Evolution, you have Truth vs. truth. I think the ID folk feel their sense of identity threatened by evolution. This makes it hard for them to even look at the evidence for evolution. I think the ID folks categorically deny the possibility of randomness. Randomness at the micro level threatens the belief that God is all good, all knowing, and all loving, but so do big things like earthquakes. The appearance of randomness and the existence of natural evil are two very good tools with which to attack the notion the God is all good, all loving, and all knowing.

# posted by

Faust : 9:21 AM

"The results in this article don't bear on the mechanism of speciation at all."

true re the excerpt, false re the whole article which as I read it suggests (implicitly, of course,) that it's about time to develop a new mantra to replace "but what about speciation?".

# posted by

Charles T. Wolverton : 12:25 PM

washerdreyer, I am not a fan of Intelligent Design theory, so I'm in no position to say what its central tenet might be. As to your claim, certainly genetic drift plus geographic isolation can produce reproductive isolates, but that process is pretty far from Darwinian evolution.

nick, if you're analyzing my psychology, my pension money is in an index fund, so randomness doesn't scare me.

# posted by

sean : 5:39 PM

"washerdreyer, I am not a fan of Intelligent Design theory, so I'm in no position to say what its central tenet might be. As to your claim, certainly genetic drift plus geographic isolation can produce reproductive isolates, but that process is pretty far from Darwinian evolution."

Um, I think that genetic drift and isolation is most definitely part of neoDarwininian theory, according to most biologists.

# posted by

gwangung : 11:30 AM