At their best, blogs tell you something you didn't know, in the same way you learn something from an interesting person you meet at a party. John Wilkins, a philosopher of science, has just such a post up at Evolving Thoughts. He addresses the strangely enduring meme, "If we evolved from monkeys, then why are there still monkeys?" While the entire post is enlightening, I was especially taken by a detail. In the mid-1700s Carl Linnaeus established the first large-scale system for classifying species. Linnaeus once declared, “There are as many species as the Infinite Being produced diverse forms in the beginning." I was aware that his religious views did not stop him from putting humans (Homo sapiens) in the primate order. It turns out, however, that Linnaeus originally put humans and chimpanzees in the same genus, Homo. Wilkins includes this striking passage from a letter Linnaeus wrote to a friend:
It is not pleasing that I placed humans among the primates, but man knows himself. Let us get the words out of the way. It will be equal to me by whatever name they are treated. But I ask you and the whole world a generic difference between men and simians in accordance with the principles of Natural History. I certainly know none. If only someone would tell me one! If I called man an ape or vice versa I would bring together all the theologians against me. Perhaps I ought to have, in accordance with the law of the discipline [of Natural History].
I had no idea that Linnaeus thought about the displeasure he would trigger by his handling of humans. It would be up to a later naturalist, Johann Blumenbach, to rip the chimps out of our genus. Today, Linnaeus's system lives on, although a bit awkwardly. Linnaeus's ability to classify humans, chimps, and the rest of life was, scientists now realize, evidence of common descent. (We belong to the mammal class because we share a common ancestor with other mammals not shared by, say, birds.) It's been some six million years since our ancestors diverged from the ancestors of chimpanzees, and our DNA remains very similar. As a comparison, consider the genus of lemurs, Eulemur. Anne Yoder of Duke University estimates that the ten species in this genus share a common ancestors that lived 9.5 million years ago. Other genuses are far older, such as the ant genus Pheidole, which dates back 60 million years. By this standard, at least, we should share a genus with chimps. Not very pleasing to some, I'd wager. But let's know ourselves, as Linneaus says. (PS: some scientists want to scrap Linnaeus's whole system and start fresh. For more, see this Discover feature by Joshua Foer.)