Planet of the Apes: Scientists probe DNA for clues on modification

One recurring theme in reader questions, especially from creationists, is that Darwinian evolution can't explain big changes - the invention of fur or feathers, kidneys or brains. These readers don't see how such innovation could possibly come about through random spelling errors in DNA, no matter how many millions of years they had to accumulate.

". . . the concept of 'descent with modification' cannot generate more complex systems . . . the old adage that if you give 1,000 monkeys 1,000 years to randomly type we could get the works of Shakespeare is false. It is not mathematically possible. We would simply get 1,000 years of gibberish," wrote one reader.

A similar complaint can be seen on creationist websites such as Answersingenesis: "Mutations are just 'typographic errors' that occur as genetic script is copied. Mutations have no ability to compose genetic sentences, and thus no ability to make evolution happen at all."

These statements ignore the ordering power of natural selection and the fact that variation comes from sources beyond simple typos.

While some look for answers in Genesis, Yale biologists Gunter Wagner and Vincent Lynch are looking in DNA. There, they have found what may be a genetic underpinning of one of the most striking leaps in our own evolutionary journey - the invention of pregnancy.

The key to this change, by which marsupials evolved into placental mammals, was not a random spelling error. Instead, a whole swath of DNA apparently invaded our mammalian ancestors' genomes 100 million years ago and copied itself thousands of times. Where this invader came from is still debated.

This is just the latest example of something biologists have known for awhile: Evolution doesn't work like monkeys at typewriters. Variation is essential for natural selection to operate, but the way variety is generated in DNA is more like a pack of monkeys using the MacBook Pro, cutting and pasting and stealing from one another like shameless plagiarists.

There are many ways that whole chunks of genetic code can be rearranged, moved, turned around, copied and pasted, and otherwise altered.

Organisms can also steal from one another, as monkeys with computers could plagiarize one another's text through the World Wide Web. But in life, the pool of genetic information is also interconnected in ways science is just beginning to understand.