The Descent of Man

After Charles Darwin completed his tour on the HMS Beagle, he returned for a time to London. It was there in 1838, during one of many visits to the London Zoo, that Darwin encountered his first orangutan, a young female named Jenny. The experience gave Darwin pause, and motivated fresh lines of thinking. "Let man visit Ouranoutang in domestication," he observed, "hear its expressive whine, see its intelligence when spoken to; as if it understands every word said—see its affection.—to those it knew.—see its passion & rage, sulkiness, & very actions of despair, . . . and then let him boast of his proud pre-eminence. . . . Man in his arrogance thinks himself a great work, worthy the interposition of a deity. More humble and I believe true to consider him created from animals."¹ The question haunting this passage was about humanity itself: where did the human end and the nonhuman begin?

In many ways, Darwin was picking up on a line of inquiry that had been broached in Scotland over half a century earlier. As Silvia Sebastiani shows in her erudite and subtle account of the Scottish Enlightenment, published in Italian in 2008 and now translated into English by Jeremy Carden, philosophers in Edinburgh, Glasgow, and Aberdeen were preoccupied not only by what distinguished the human from the nonhuman, but also by divisions within humanity itself. Were men—and, by extension, women—originally descended from a single species, in accordance with biblical wisdom, or were multiple species the point of origin for men in all of their human diversity? This was a high stakes debate, with no easy answers. To be on the side of "monogenism" was to favor a more universalistic conception of humanity, with differences perceived less as the product of nature than of climate and history. To be on the side of "polygenism," however, was to favor—usually, but not always—a tendency toward hierarchical, racialized thinking, with a sense that individual and national destinies were inscribed on the physical body.

Like Darwin at the London Zoo, Scottish philosophers were clearly prompted by what they had read and witnessed. By the eighteenth century, "difference" was no longer an abstract philosophical consideration. The slave trade was entering its most aggressive—and ignominious—phase. British scientists and adventurers, meanwhile, were fanning out across the globe, sending dispatches home from Asia, Africa, the Americas, and the South Seas. Non-Westerners, in turn, were increasingly making their way to London, Edinburgh, and other European urban centers. As Catherine Molineux and Kate Fullagar have both recently shown, there were plenty of opportunities for cross-cultural exchanges in Georgian Britain's own tobacco shops, public squares, and city streets.² This sociocultural backdrop is generally assumed rather than elucidated in Sebastiani's account. But it shapes the way she reads her materials, and gives her text a refreshing sense of urgency. In teasing out the sometimes maddeningly complex ways in which these Scottish men—and they were, by Sebastiani's account, universally men—responded to the problem of difference, she makes clear that their ideas had a profound impact in the world.

The book itself is organized around a series of philosophical problems and disagreements, covering a period from the mid-eighteenth century to the 1780s. Sebastiani begins by considering Montesquieu (a monogenist) and Hume (a polygenist), whose philosophical encounter in 1748, she persuasively claims, set the terms for all subsequent Scottish Enlightenment treatments of cultural, racial, and gender difference. Surely, Montesquieu's Esprit des lois and Hume's essay "Of National Characters" could not have offered more sharply diverging accounts of human diversity. While Montesquieu assigned climate near total explanatory power in his analysis, Hume asserted that fundamental "natural" differences existed between peoples. This conclusion led Hume to assert, in a now infamous footnote that he later appended to his essay in 1753–54, that he was "apt to suspect the negroes and in general all other species of men (for there are four or five different kinds) to be...