It's Charles Darwin's 200th birthday, and we still don't know why humans and chimps share 99 percent of their DNA, yet are such different animals. A new study published today advances a weird new theory.

A group of researchers at the University of Washington have discovered that there is one area where human and ape DNA mutated very rapidly during the time that they were diverging on the evolutionary tree. Both species' genomes mutated a great deal in areas where there are a lot of repeat sequences of DNA. Humans, like most creatures, have areas of their genome where the same chunk of genetic code is repeated once or several times.

According to the University of Washington, lead researchers Tomas Marques-Bonet and Jeffrey M. Kidd said:

The new study shows big differences in the genomes of humans and great apes within duplicated sequences containing rapidly evolving genes. Most of these differences occurred at a time just prior to the speciation of chimpanzee, gorilla, and humans.

So is it possible that the reasons for such dramatic differences between human and chimp can be traced back to these quickly-mutating repeat regions?

According to the University of Washington:

Chimps and people share almost 99 percent of the non-duplicated sequences of their genomes; their proteins are virtually identical; and there are very few rearrangements that distinguish ape-human chromosomes. In contrast, the researchers noted that the duplicated sequences show much more variation than the other portions of the genetic code.

But this is such a new area of research that we need to be cautious before drawing any firm conclusions. While this looks like a promising avenue for further inquiry, the researchers explained:

There is still no final answer as to why chimps and humans are different. Maybe segmental duplications that are specific to humans are another layer to explore, or maybe the distinction between human and chimps is not found in these genetic differences. What is certain is that genetic differences contribute significantly to what makes a human and chimp different, and we know that these regions of our genetic code are changing much more rapidly than most others. The next challenge will be making sense of all these differences and the genes that are affected by them.

While previous studies have suggested that we will learn more about ourselves by studying so-called junk DNA, or DNA that doesn't seem actively involved in coding for proteins. But this new work suggests we study the parts of our genetic code that repeat themselves. These odd, repeated segments of our DNA may be the key to understanding why we mutated into the hairless, neurotic hominids we are, instead of turning into happy-go-lucky bonobos.


University of Washington