The Fruit, the Tree, and the Serpent:  Why We See So Well, by Lynn Isbell (Harvard)

Reviewed by Benjamin Schwarz

April 2010 ATLANTIC 

The anthropologist and animal behaviorist Lynne Isbell elegantly posits here that the human facility with language evolved largely thanks to snakes. Coolly testing hypotheses and assessing evidence across an impressive range of disciplines—neuroscience, primate behavior, paleogeography, molecular biology, and genetics—she argues that our distant primate relatives developed their exceptional ability to see and identify “objects that were close by and in front of them” in order to detect and avoid what was almost certainly their most dangerous predator—the snake. This unique visual acuity led indirectly (to crudely oversimplify) to the peculiar evolutionary path of primate brains. Furthermore, as Isbell points out, of all the species, only humans point declaratively, and we are much better at following the pointing of others to our visual periphery than to our visual center, and while looking down rather than up. “What was it outside central vision and in the lower visual field that was so urgent for our ancestors to see that it caused neurological changes to enable us to turn automatically in the direction of a gaze and a pointing finger?” Isbell asks. Her answer: snakes. “I cannot think of any other object in the lower visual field that would have been more difficult to see and more unforgiving if missed.” The relationship between declarative pointing and the evolution of language is so strong, neurological and cognitive studies find, that the two are, to a degree, interchangeable. And so, Isbell avers, Genesis has it right: the snake made us human. This groundbreaking, intellectually scintillating work is nonfiction at its absolute best. Isbell ranges widely, unpacks her evidence meticulously, synthesizes disparate and difficult material economically, addresses counterarguments scrupulously, and writes cleanly, often gracefully, and occasionally even playfully.