The Gene: An Intimate History - Siddhartha Mukherjee Page 0,31

to systematically measure human features and analyze them using statistical methods. Quetelet’s approach was rigorous and comprehensive. “Man is born, grows up and dies according to certain laws that have never been studied,” Quetelet wrote. He tabulated the chest breadth and height of 5,738 soldiers to demonstrate that chest size and height were distributed along smooth, continuous, bell-shaped curves. Indeed, wherever Quetelet looked, he found a recurrent pattern: human features—even behaviors—were distributed in bell-shaped curves.

Galton was inspired by Quetelet’s measurements and ventured deeper into the measurement of human variance. Were complex features such as intelligence, intellectual accomplishment, or beauty, say, variant in the same manner? Galton knew that no ordinary measuring devices existed for any of these characteristics. But where he lacked devices, he invented them (“Whenever you can, [you should] count,” he wrote). As a surrogate for intelligence, he obtained the examination marks for the mathematical honors exam at Cambridge—ironically, the very test that he had failed—and demonstrated that, to the best approximation, even examination abilities followed this bell-curve distribution. He walked through England and Scotland tabulating “beauty”—secretly ranking the women he met as “attractive,” “indifferent,” or “repellent” using pinpricks on a card hidden in his pocket. It seemed no human attribute could escape Galton’s sifting, evaluating, counting, tabulating eye: “Keenness of Sight and Hearing; Colour Sense; Judgment of Eye; Breathing Power; Reaction Time; Strength and Pull of Squeeze; Force of Blow; Span of Arms; Height . . . Weight.”

Galton now turned from measurement to mechanism. Were these variations in humans inherited? And in what manner? Again, he veered away from simple organisms, hoping to jump straight into humans. Wasn’t his own exalted pedigree—Erasmus as grandfather, Darwin as cousin—proof that genius ran in families? To marshal further evidence, Galton began to reconstruct pedigrees of eminent men. He found, for instance, that among 605 notable men who lived between 1453 and 1853, there were 102 familial relationships: one in six of all accomplished men were apparently related. If an accomplished man had a son, Galton estimated, chances were one in twelve that the son would be eminent. In contrast, only one in three thousand “randomly” selected men could achieve distinction. Eminence, Galton argued, was inherited. Lords produced lords—not because peerage was hereditary, but because intelligence was.

Galton considered the obvious possibility that eminent men might produce eminent sons because the son “will be placed in a more favorable position for advancement.” Galton coined the memorable phrase nature versus nurture to discriminate hereditary and environmental influences. But his anxieties about class and status were so deep that he could not bear the thought that his own “intelligence” might merely be the by-product of privilege and opportunity. Genius had to be encrypted in genes. He had barricaded the most fragile of his convictions—that purely hereditary influences could explain such patterns of accomplishment—from any scientific challenge.

Galton published much of this data in an ambitious, rambling, often incoherent book—Hereditary Genius. It was poorly received. Darwin read the study, but he was not particularly convinced, damning his cousin with faint praise: “You have made a convert of an opponent in one sense, for I have always maintained that, excepting fools, men did not differ much in intellect, only in zeal and hard work.” Galton swallowed his pride and did not attempt another genealogical study.

Galton must have realized the inherent limits of his pedigree project, for he soon abandoned it for a more powerful empirical approach. In the mid-1880s, he began to mail out “surveys” to men and women, asking them to examine their family records, tabulate the data, and mail him detailed measurements on the height, weight, eye color, intelligence, and artistic abilities of parents, grandparents, and children (Galton’s family fortune—his most tangible inheritance—came in handy here; he offered a substantial fee to anyone who returned a satisfactory survey). Armed with real numbers, Galton could now find the elusive “law of heredity” that he had hunted so ardently for decades.

Much of what he found was relatively intuitive—albeit with a twist. Tall parents tended to have tall children, he discovered—but on average. The children of tall men and women were certainly taller than the mean height of the population, but they too varied in a bell-shaped curve, with some taller and some shorter than their parents.I If a general rule of inheritance lurked behind the data, it was that human features were distributed in continuous curves, and continuous variations reproduced continuous variations.

But did a law—an underlying pattern—govern the genesis of variants? In the late 1880s, Galton boldly