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James R. Flynn’s observation that IQ scores experienced dramatic gains from generation to generation throughout the 20th century has been cited so often, even in popular media, that it is becoming a cocktail party talking point. Next stop a New Yorker cartoon. (An article about Flynn and the Flynn effect has already been published in The New Yorker.)

A recent report in Trends in Genetics (part 1 and part 2) takes a bleaker view of our cognitive future—one that foresees the trend line proceeding inexorably downward. Gerald Crabtree, a biologist at Stanford University, has put forward a provocative hypothesis that our cushy modern existence—absent the ceaseless pressures of natural selection experienced during the Paleolithic—makes us susceptible to the slow creep of random genetic mutations in the the 2000 to 3000 genes needed to ensure that our intellectual and emotional makeup remains intact. The implications of this argument are that we as a species of the genus Homo are over many generations slowly losing our sapiens.

The really clever part of Crabtree’s argument rests on the contention that a Stone Age Fred Flintstone may have been more of a dynamo in some ways than a 20th century Albert Einstein—our pre-historic forebears performed the evolutionary heavy lifting that led to the swollen heads that we still avail ourselves of, at least until the inevitable decline predicted by Crabtree sets in.


Expansion of the human frontal cortex and endocranial volume, to which we likely owe our capacity for abstract thought, predominately occurred between 50 000 and 500,000 years ago in our prehistoric African ancestors, well before written language and before we had the modern voice-box to produce sophisticated verbal language, but after the first tools. Thus, the selective pressures that gave us our mental characteristics operated among nonverbal hunter-gatherers living in dispersed bands or villages, nothing like our present-day high-density, supportive societies.

In line with Crabtree’s take, the transition to survival through wiles—in place of speed and physical strength—required adaptations that appeared to rival or outpace the most lofty contemporary intellectual achievements like writing a symphony or cogitating on higher math. One small error in gauging the aerodynamics and gyroscopic stabilization of a spear and one of our would-be ancestors became a canape for a saber-tooth tiger.

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Many kinds of modern refined intellectual activity (by which our children are judged) may not necessarily require more innovation, synthesis, or creativity than more ancient forms: inventing the bow-and-arrow, which seems to have occurred only once about 40,000 years ago, was probably as complex an intellectual task as inventing language. Selection could easily have operated on common (but computationally complex) tasks such as building a shelter, and then computationally simple tasks, such as playing chess, became possible as a collateral effect.

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Without the rigors of strong selection in our extended urban conglomerates—no more necessity of getting it right the first time on that spear throw—the slow but relentless decline of those 2,000 to 5,000 cognition-related genes has already begun—as this argument goes. Crabtree begins the first part of his essay by asserting that the average citizen from Athens circa 1,000 B.C.—or anyone from Africa, India, Asia or the Americas millenia back—would be among the “brightest and most intellectually alive of our colleagues and companions, with a good memory, a broad range of ideas, and a clear-sighted view of important issues”—personal qualities supplemented by an astonishing emotional aplomb. This hyper-fit type would have prevailed even before the rise of civilization:


A hunter–gatherer who did not correctly conceive a solution to providing food or shelter probably died, along with his/her progeny, whereas a modern Wall Street executive that made a similar conceptual mistake would receive a substantial bonus and be a more attractive mate. Clearly, extreme selection is a thing of the past.

Maybe this explains our fascination with post-apocalyptic Mad Max-style fantasies? But where’s the proof for Crabtree’s musings and what about contradictory evidence? Crabtree proposes a test of his hypothesis and he also dismisses the Flynn effect that suggests that we have been getting progressively smarter generation after generation. Better IQ scores, Crabtree posits, are not a result of natural selection, but rather may have resulted from getting rid of lead and other heavy metals from gasoline and paint, from elimination of hypothyroidism by putting iodine in salt and from learning how to take tests better. Notwithstanding the Flynn effect, our slow genetic decline continues apace.Much more at http://blogs.scientificamerican.com/talking-back/2012/11/26/homo-sans-
sapiens-is-dumb-and-dumber-our-evolutionary-destiny/

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