The Gap: The Science of What Separates Us from Other Animals
by Thomas Suddendorf
Basic Books, 2013

As recently as 30,000 years ago, several species of upright-walking, intelligent hominins shared the earth with our ancestors. Tiny Homo floresiensis made stone tools on the island of Flores in Indonesia, Denisovans inhabited caves in southern Siberia, and Neandertals, with brains at least as large as our own, ranged across Ice Age Europe and the Middle East. They learned to survive in the cold, used fire, wore clothes, cared for the sick, buried the dead and maybe even wore jewelry. These fellow members of the genus Homo most likely shared many qualities we now deem uniquely human. We can claim to be exceptional among the animals, psychologist Suddendorf writes, only because our closest relatives have gone extinct.

In The Gap, Suddendorf examines the apparent chasm that separates humans from other animals. He covers six domains—language, mental time travel (thinking about the past and future), theory of mind (thinking about thinking), intelligence, culture and morality—in which multitudes of clever studies have probed the minds of animals and, for comparison, young children. What does it mean that great apes can recognize themselves in the mirror and monkeys cannot? Whales learn songs from one another, but does that count as culture?

“If you set the bar low,” Suddendorf writes, “you can conclude that parrots can speak, ants have agriculture, crows make tools, and bees cooperate on a large scale.” He sets the bar higher. Although he presents both “romantic” and “killjoy” interpretations of animal ability, his sure-handed, fascinating book aims neither to exaggerate the wisdom of animals nor to promote the exceptionalism of human beings.

Instead Suddendorf distills the gap into two overarching capacities: the ability to imagine different scenarios beyond what our senses perceive and a strong drive to link our minds together, by looking to one another for information or understanding. These two capacities transform common animal traits into distinctly human ones: communication into language, memory into planning, and empathy into morality. Suddendorf reminds us that many extinct hominins shared both capacities, making them more similar to us than to the great apes.

Ultimately, taking measure of the current gap may be less important than understanding how it came to be. Genetic evidence shows some interbreeding between Homo sapiens and Neandertals. Nevertheless, we very likely had an unfriendly hand in their extinction, through violence or competition. Suddendorf, exercising his own fine scenario-building skills, asks whether we will continue to widen the gap by driving the great apes, already endangered, to extinction. Will our grandchildren think themselves more extraordinary for having monkeys as their closest living relatives?