In the view of Wynn and Coolidge—an archaeologist and a psychologist who form an unusual scientific partnership—a stepwise increase in working memory capacity was central to the evolution of advanced human cognition. They argue that the final steps, consisting of one or more genetic mutations that led to "enhanced working memory," happened sometime after our species appeared nearly 200,000 years ago, and perhaps as recently as 40,000 years ago. With enhanced working memory, modern humans could do what their ancestors could not: express themselves in art and other symbolic behavior, speak in fully grammatical language, plan ahead, and make highly complex tools.Not everyone is buying this theory, because it's supported by rather sparse data, and because it's not clear which came first, enhanced memory or advanced human cognition, but the theory is making a splash nonetheless.
Despite the critics, Wynn and Coolidge's ideas are increasingly popping up in scientific journals. The pair "have made a really big splash," says Philip Barnard, a cognition researcher at the University of Cambridge in the U.K. This month, Current Anthropology devotes a special online supplement to the topic, and later in April, Wynn and Coolidge will update their ideas at a major meeting on the evolution of language in the Netherlands. The theory makes sense to many. "It is the most impressive, explicit, and scientifically based model" so far, says archaeologist Paul Mellars of the University of Cambridge.
But we aren't here to debate the merits of this theory. We're here to point out that in a broader, and more serious sense......it's bunkum! Cognition, whatever its molecular and neurobiological nature is, is only one in a long string of human capabilities that have been advocated to be The One that made us what we are.
So, not only our memory, but fire, domesticated dogs, brain size, opposable thumbs, the FOXP2 gene ('for' language), neotenous birth, altered birth canal, the microcephalia gene, among many other traits, behaviors, or genes have been posited as 'the' thing that made us human. Because of natural selection, naturally.
Each of these theories can be backed up by a story that logically (usually) makes sense. Each refers to genuine human traits that are quite different from the corresponding traits in our closest primate relatives. So far so good, and understanding these traits is a fine and important thing to do. But it's curious that each trait is so often just one thing taken in isolation -- and that that one thing is often the researcher's particular area of expertise.
But, there was no single point in time when we became human. And no single trait evolved in isolation, or simply in response to another. The traits evolved in a higgelty-piggelty way, mosaic changes in varying physical, metabolic, and neurological patterns. Without upright posture, our kind of tool use would not have evolved. That means useful thumbs. Upright posture means various other anatomical changes. Without these, there'd be no need for our kind of brain power. Language, symbolic behavior verbal and otherwise, went hand in hand (or thumb in thumb?) with these other changes. This is what's interesting about how evolution works. The fact that everything evolves together -- must co-evolve -- which of course is true of every species, not just humans. Even if something like the enhanced memory theory "makes sense to many", it's nonsense to treat these traits in isolation.
And, evolution doesn't work by leaps, which is what most of these theories in effect would require: A point in time when a new thumb form or a tame wolf was enough to allow its owner to have more children than those in his or her small band who were less well-endowed, a kind of luck that would have had to carry on for many generations. All the kinds of traits that are posited as the one that made us human are complex, they evolved slowly over many millennia, and they generally arose together. The idea that we should be able to attribute our "humanness" to a single gene or trait -- a kind of 'Master' trait, which would have had to precede the others -- involves precisely the same determinism and darwinian fundamentalism that we so frequently criticize.
It was long ago -- in 1929 -- when the Taung specimen was unearthed in South Africa. That specimen showed that, contrary to our egotistical preconceptions, the noble (gratuitously greedy and murderous?) human brain, did not lead the way. Upright posture of a sort evolved first. Culture evolved along the way, bit by bit, and does not require a huge brain per se. Trying to hawk MyFavoriteTrait is good for making a news splash, but is misleading science. Fortunately, while it helps build careers, most of the nonsensical aspects quickly fade. Meanwhile, those who are serious about human evolution can ignore the carnival barking and study the traits in a more sober evolutionary sense.