In the most recent post on this page (I’ve Mind, Hive Mind), I wrote that “our intellects are unique, in the sense that no other animal more than remotely approaches the power of the human brain.”
Chip Walter made a strong case for this claim in his excellent, soon-to-be-published book, Last Ape Standing (which I recently reviewed on my BOOKS page). Now a new study, published in the Proceedings of the Royal Society B, gives empirical support to the idea.
Walter writes that “the imponderable forces of evolution had made a bet that delivered not greater speed or ferocity, not greater endurance or strength, but greater intelligence, or put in flat Darwinian terms, greater adaptability.” He explains that larger, more complex brains give us “a cerebral suppleness,” a flexible and adjustable response to circumstances. Because our brains are so plastic, and our cerebrations so malleable, we are not as subject to the instinct-driven limitations that restrain all other species,
Walter argues that we are born with brains that have not fully developed, and that this apparent flaw is, in fact, our greatest mental strength. Our brains develop in response to our environments. We absorb sensory experience on one hand and complex cultures on the other during the first months and years of our lives, and it’s the ways that these inputs shape the connections in our brains that drives everything from social behaviour to artistic creativity. It is this extended plasticity, Walter writes, that makes us unique:
A thirty-six-month-old child’s brain is twice as active as a normal adult’s, with trillions of dendrites and axons making contact, jabbering and listening and tightening the collaborative party that makes the human mind possible.
In ‘Human Intelligence Secrets Revealed by Chimp Brains” (New Scientist, December 18), Tia Ghose reports: “Unlike the case in human brains, neural connectivity does not rapidly augment in chimpanzee brains during the first two years of life, which may explain our unique intelligence.”
The new results, published today (Dec. 18) in the Proceedings of the Royal Society B, partly explain why humans are so much brainier than our nearest living relatives. But they also reveal why the first two years of life play such a key role in human development.
The PRS(B) study compared the brains of chimpanzees and human infants, finding that “humans undergo a massive explosion in white matter growth, or the connections between brain cells, in the first two years of life.
Researchers in Japan (where restrictions on experiments with live chimpanzees were adopted later than in the U.S.) compared MRI scans of three chimps, from birth to six years of age. They compared these scans with scans for six macaques and 28 children. Both the chimpanzees and the human children had more early brain development than did the macaques, showing that “the increase in total cerebral volume during early infancy and the juvenile stage in chimpanzees and humans was approximately three times greater than that in macaques.”
Despite the fact that our closest primate relatives also experience substantial brain expansion during their first few years of life, human brain expansion was characterized by “explosive growth in the connections between brain cells, which manifests itself in an expansion in white matter. Chimpanzee brain volumes ballooned about half that of humans’ expansion during that time period.”
While the findings were expected, this is the first time that researchers have been able to study the same individuals over an extended period of early childhood. And the results reinforce Walter’s claim that we are so adaptable, so flexible, so creative, because we are born with “incomplete” brains. This incompleteness lets our environments and our cultures stimulate and direct much of the wiring of our brains, and, as one neuroscientist suggests at the end of the New Scientist article, “That opens an opportunity for environment and social experience to influence the molding of connectivity.”
One thing that stands out for me about this latest study is how much it reconfirms the view that human qualities, including the characteristics of that mysterious thing we call the “human mind,” are unique in power but not in kind.
Yes, we are special beings. But our specialness comes from our extreme abilities with regard to functions and anatomical features that we share with other animals. Once again we find evidence that we are not some sort of “special creation” but special creatures — more able than other creatures, but creatures nonetheless.
It shouldn’t be necessary to keep repeating this idea, but my own experience is that there are too, too many people out there who don’t want to hear anything that threatens the self-congratulatory illusion that we’re not “just animals.” Sometimes, especially in the opinions of the declared religious, the dedication to a special human dignity is stated directly; in other cases, even in the writings of declared atheists, the special human bias leaks out as a kind of unspoken dualism, or as a claim that we are too complex, too mysterious, ever to be understood. Both positions are, in my view, simply wrong — and too often self-deluding.
Sorry, guys, but we are just animals. As it turns out, pretty special ones.