2. Crude Oldowan tools—made by just a few blows to a core stone to create an irregular edge—emerged 2.4 million years ago and were probably made by
3. Why was there a sudden explosion—what Jared Diamond, in his book
4. Humans are often called the “Machiavellian primate,” referring to our ability to predict other people’s behavior and out-smart them. Why are we humans so good at reading one another’s intentions? Do we have a specialized brain module, or circuit, for generating a theory of other minds, as proposed by the British cognitive neuroscientists Nicholas Humphrey, Uta Frith, Marc Hauser, and Simon Baron-Cohen? Where is this circuit and when did it evolve? Is it present in some rudimentary form in monkeys and apes, and if so, what makes ours so much more sophisticated than theirs?
5. How did language evolve? Unlike many other human traits such as humor, art, dancing, and music, the survival value of language is obvious: It lets us communicate our thoughts and intentions. But the question of how such an extraordinary ability actually came into being has puzzled biologists, psychologists, and philosophers since at least Darwin’s time. One problem is that the human vocal apparatus is vastly more sophisticated than that of any other ape, but without the correspondingly sophisticated language areas in the human brain, such exquisite articulatory equipment alone would be useless. So how did these two mechanisms with so many elegant interlocking parts evolve in tandem? Following Darwin’s lead, I suggest that our vocal equipment and our remarkable ability to modulate our voice evolved mainly for producing emotional calls and musical sounds during courtship in early primates, including our hominin ancestors. Once that evolved, the brain—especially the left hemisphere—could start using it for language.
But an even bigger puzzle remains. Is language mediated by a sophisticated and highly specialized mental “language organ” that is unique to humans and that emerged completely out of the blue, as suggested by the famous MIT linguist Noam Chomsky? Or was there a more primitive gestural communication system already in place that provided scaffolding for the emergence of vocal language? A major piece of the solution to this riddle comes from the discovery of mirror neurons.
I HAVE ALREADY alluded to mirror neurons in earlier chapters and will return to them again in Chapter 6, but here in the context of evolution let’s take a closer look. In the frontal lobes of a monkey’s brain, there are certain cells that fire when the monkey performs a very specific action. For instance, one cell fires during the pulling of a lever, a second for grabbing a peanut, a third for putting a peanut in the mouth, and yet a fourth for pushing something. (Bear in mind, these neurons are part of a small