Why Chimps Can’t Talk

Chimpanzee 1: Help! The human’s about to escape.

Troy: Get your paws off me, you dirty ape!

Chimpanzee 2: (gasp) He can talk!

Orangutans: He can talk! He can talk! He can talk!
He can talk! He can talk! He can talk!
Troy: And I can siiiiiiiiiiing!

Chimp Nurse: Oooh! Help me, Dr. Zaius!

Orangutans: Dr. Zaius! Dr. Zaius!
Dr. Zaius! Dr. Zaius!
Dr. Zaius! Dr. Zaius!
O, Dr. Zaius!

In one of the most entertaining episodes ever, the hit TV series The Simpsons recreated the movie Planet of the Apes as a musical. Here’s a video (courtesy of FOX Broadcasting) of a topsy-turvy world where chimpanzees can talk and humans can’t:

For many years, it was thought the tool usage differentiated man from ape. "I suppose the first really significant thing that the world heard about was chimpanzees using and making tools,” says groundbreaking primatologist Dr. Jane Goodall. “It was thought that only humans did this and that this set us apart from the rest of the animal kingdom." It turns out that complex language – not tool usage – is what really differentiates us from our chimpanzee brethren. (A concept The Simpsons spoof clearly stands on its head.)

The findings… could help explain a significant part of the difference between human and chimpanzee brains –- just two small differences in one gene…

Now, genetic evidence may show how our language brain circuitry came about over the last half million years of human evolution. In a study published in Nature, Neuroscientists Genevieve Konopka and Daniel Geschwind at the University of California, Los Angeles have demonstrated that the human version of the FOXP2 gene –- one that mutated around the time humans developed the ability to talk –- regulates more than 100 other genes differently than the chimpanzee version of the gene. Other genes may also be involved, but there’s a good chance that this mutation helped us humans develop speech and language.

To test what Foxp2 does differently in humans, Konopka and Geschwind grew human brain cells lacking Foxp2 in Petri dishes. To some, they added human Foxp2 and to others the chimp version. They then recorded all the genes that were affected. Out of the hundreds of genes controlled by Foxp2, they identified 116 that responded differently to the human version of Foxp2.

New Scientist reports that evolutionary studies of Foxp2 suggest that it acquired its human-specific changes during the last half million years of human evolution and that this is roughly when language may have emerged. Geschwind’s preliminary studies of the evolution of the 116 genes affected by Foxp2 show a possible common ancestry. "It brings up the possibility, which is not at all remote, that these genes may have evolved in concert," he says. "Either Foxp2 itself is pretty damn important," he continues, "or it’s part of a regulatory circuit –- something else is regulating Foxp2 that no one else has found yet."

Chimp not speaking with DNA background

While the results suggest a central role for Foxp2 in the evolution of language, Geschwind cautions against calling it "the language gene.” The findings are preliminary, although they could help explain a significant part of the difference between human and chimpanzee brains –- just two small differences in one gene, according to Wolfgang Enard at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. "That would be really amazing," says Enard.

According to another recent study led by Chet Sherwood, a neuroscientist at George Washington University in Washington DC, a brain region critical to speech and language in humans developed substantially after humans split from chimpanzees. French physician Pierre Paul Broca identified this region of the brain studying brain-damaged patients incapable of uttering more than a few words. “Broca’s area” typically occupies a much larger portion of the left half of the human brain than the right. Because right-handed humans also tend to process language in their left halves (this is reversed for lefties), some researchers think that lop-sidedness in Broca’s area may help explain why humans –- and not chimpanzees –- developed language. Broca’s area ballooned disproportionately during our species’ evolution. Human brains are 3.6 times larger than those of chimpanzees, on average. And Broca’s area is more than 6 times larger in humans than chimpanzees according Natalie Schenker, a neuroscientist at the University of California, San Diego, who worked with Sherwood on the research. Marc Hauser, a professor of human evolutionary biology at Harvard University, cautions that it’s too early to draw too many conclusions regarding the genetic basis of the evolution of language circuitry in humans. "I would be extremely skeptical about drawing inferences," says Hauser.

Why did humans acquire complex language circuitry when chimpanzees did not? Both the Foxp2 gene and Broca’s area seem implicated in these recent studies. What’s clear is that the upside down world of Planet of the Apes – where chimps evolve complex speech – is highly improbable, even if humans and chimps were to interbreed. Here’s a humorous video called “Humanzees” (courtesy of Discovery News) that explores that somewhat horrifying possibility:

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