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Evolution Did Not Snap the Brain Together like LEGOS


Human cognition is more than a legacy of our Paleolithic past

Evolutionary psychology has typically tried to identify the piece parts of human cognition shaped by the rigors of natural selection. New questions have arisen in this contentious discipline about what exactly is on that parts list—or whether the list itself really exists.

One of the foremost debating points centers on whether the brain consists of a series of Lego-like modules, each one produced from evolutionary adaptations that resulted in mental tools for things like going after Mastodons, forming clans and communicating the daily incidentals related to food, shelter and mating. Another way to think about all this is to invoke the metaphor of a Swiss-Army knife, with each adaptive module the equivalent of a corkscrew, nail clipper or a myriad of cutting implements.

The revisionist viewpoint rejects this neat tailoring of mental functioning championed by psychologists like Leda Cosmides and John Tooby. Instead, upstarts trot out the human hand as a replacement analogy for the pocket knife, a single all-purpose implement that can poke, prod, pull and push. A walk through the new thinking on evolutionary psychology appears in the Aug. 5 edition of the Philosophical Transactions of the Royal Society of London B. (The original journal, founded in 1665, was the first anywhere to deal solely with science—and this issue is open to everyone for a download.)

The metaphor of the hand, notes Cecilia Heyes of Oxford in an introductory article, alludes to the ability of a limb extension that can "strip the defensive spines from a piece of fruit, making it safe to eat, but in Thai dancing it can also signal the smallest nuances of emotion. The human hand performs with equal facility a vast array of tasks that natural selection did and did not 'foresee'."

The hand analogy translates into sub-cranial physiology. On the most basic level, the new view holds that the brain did not develop through a dichotomy between higher brain functions and the automatic reflexes that enable us to catch a baseball. This can be witnessed in the neocortex and the cerebellum—executive control in the neocortex ("Don't hit that jerk!") is not an evolutionary plug-in that evolved independently from the sensorimotor functions of the cerebellum. Says Heyes: "The co-evolution of these structures not just in primates, but over deep evolutionary time—in all mammalian lineages—implies that in evolutionary terms the division between higher and sensorimotor intelligence, between thinking and acting, is artificial." In other words, it's all one big integrated system that takes on a functional identity when responding to the environment—a form of interaction to which academics bequeath the ponderous term "embodied cognition."

Traditionalists assert that our Stone Age forbears developed a set of planning skills— "conceptual abstraction"— to befuddle and ultimately overpower prey. The revisionist argument counters that these and facets of cognition existed at least six million years ago in the common ancestor of chimps and humans and therefore were not just the equivalent of downloadable apps that turned up millions of years later with the arrival of the Stone Age. The evolutionary line that ultimately led to the invention of the iPhone did refine these capabilities to enhance social interactions to an extent not found in chimps, enabling hunter gatherers in the Flintstone era to function as a "unique and highly competitive predatory organism." But both the chimp and hominid lines tended in the same direction.

The new Evo-Psych also affords a new place at the table to cultural evolution, with a lexicon influenced by the world of the gene: "differential copying of instances of cultural variants." The totality of this emerging view of cognition replaces "special-purpose cognitive gadgets," subject to little influence from the environment, with "domain-general" thinking machines that use a common set of computations for everything from tool-making, to mentalizing to imitating others. The nouveau Evo lends a hand to explicating how we resolve everyday social and technical problems encountered when this general-purpose cognitive maquina encounters the world beyond the eyeballs.

Source: The Wonderful Paleo Art of Heinrich Harder








The views expressed are those of the author and are not necessarily those of Scientific American.

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