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The Debunker: Did Humans Evolve from Monkeys?

by Ken Jennings

According to the Chinese zodiac, it's been the "Year of the Goat" since last February, and we're getting pretty tired of the nonstop goat-related festivities. Luckily, the lunar new year this month begins the "Year of the Monkey," so the future looks bright. But Jeopardy!'s Ken Jennings tells us that a lot of stuff we thought we knew about our mischievous treetop friends is just bananas. All month, he'll be here to put a stop to all the monkey business.

The Debunker: Did Humans Evolve from Monkeys?

In The Origin of Species, Charles Darwin was careful never to apply his new theory of "natural selection" to the origin of man, but readers were quick to connect the dots. Before the book was even published, minister John Leifchild was complaining in the Athenaeum about the new "belief that man descends from the monkeys." This caricature of evolutionary theory was so fixed in the public mind that the 1925 trial of John Scopes, for teaching evolution in small-town Tennessee, is still known as the "Scopes Monkey Trial." Prosecuting attorney William Jennings Bryan got big laughs during the trial for reading excerpts from The Descent of Man and then complaining to the crowd that, according to Darwin, humans were descended "not even from American monkeys, but from Old World monkeys!"

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We now know that Bryan's two families of monkeys (Old World vs. New) diverged 40 million years ago, but that back then these proto-primates didn't bear much resemblance to modern monkeys. At the time, they were just 20 million years or so removed from their squirrel- or shrew-like ancestors, and probably looked more like modern lemurs. After another 20 million years, the first apes evolved, and just seven million years ago, early hominids began to diverge from the chimpanzees and bonobos, our nearest genetic cousins.

In other words, it's not correct to say that humans evolved from monkeys, but rather that humans and monkeys both evolved from a common ancestor—not anything we'd recognize as a "monkey," but some proto-primate that no longer exists. The problem with the "humans evolved from monkeys" straw-man (or straw-monkey) argument is that it often leads the evolution skeptic to ask, "Well then, why are there still monkeys?" The right answer to this question is, "Because apes and humans are an isolated offshoot from monkey-like ancestors, and we didn't out-compete our fellow descendants into extinction... yet." But if the questioner is religious, it may save time to say something like, "If Protestants arose from Catholics, then why are there still Catholics?"

Quick Quiz: John Scopes was actually not a full-time science teacher at Rhea County High School—he was just a substitute. What was his real job at the school?

Ken Jennings is the author of six books, most recently his Junior Genius Guides, Because I Said So!, and Maphead. He's also the proud owner of an underwhelming Bag o' Crap. Follow him at ken-jennings.com or on Twitter as @KenJennings.