Chimps More Evolved Than Humans?

April 16, 2007 — A comparison of human and chimpanzee genes has revealed a startling possibility: chimps may have evolved more than humans in the 6 or 7 million years since both diverged from a common ancestor.

A study comparing human and chimp genes that appear to have evolved since we parted ways shows that humans have about 154 such genes and our nearest primate relative a whopping 233.

This implies that chimps have undergone more evolutionary changes than humans over the same period of time. It also underscores a common misunderstanding that if an animal is "more evolved" it must be smarter or superior to others in some way.

"This just shows us that we're ordinary animals," said Jianzhi Zhang, an evolutionary biologist at the University of Michigan. Zhang and his colleagues published their study in the current issue of the Proceedings of the National Academy of Sciences.

In evolutionary terms, more changes in chimps might simply reflect that until a few thousand years ago there were a lot more chimps on Earth than humans, so they had a bigger gene pool and therefore more opportunities for change, Zhang explained to Discovery News.

It could also just reflect that chimps were forced to adapt to more things than humans. Just what, exactly, is unknown, but it clearly did not lead to a larger brain or any of the other adaptations that set humans apart from other mammals.

The "bottom line is that this study underlines the risks of making generalizations about human evolution," said Ajit Varki, a professor of cellular and molecular medicine at the University of California at San Diego.

"Humans only emerged once, after many complex stages of hominid evolution, and there is no reason to assume that the most logical explanations (for our evolution) will actually turn out to be right," he added. "And the final answers are likely to be far more complex than we currently think they are."

The new study is hardly the last word on the matter, said Varki. There are many ways genes can come and go, and affect evolution.

"In the end there will be no substitute for looking into the details of each gene difference from the functional perspective," said Varki. "It could well turn out that the deletion of a specific gene or a single critical amino acid encoding change in a gene has more biological significance than a large number of genes that at first glance seem to have undergone a lot of changes."