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Space to Think, a new book celebrating ten years of the Dublin Review of Books More Information 

The Unpredictable Species, What Makes Humans Unique

Philip Lieberman



The design principles that guided the evolution of the human brain are similar. Ernst Mayr, who shaped twentieth-century evolu­tionary and genetic research, repeatedly pointed out the "proximate logic of evolution." Existing structures and systems are modified sometimes elegantly, sometime weirdly, to carry out new tasks. Our capacity for innovation, which distinguishes human behavior from that of any other species, living or extinct, is a product of this mini­mal-cost design logic.

The path of human evolution diverged from chimpanzees, our closest living relatives, five to seven million years ago. The brains of our distant ancestors had started to enlarge a million years ago, but big brains alone don't account for why we act and think in a manner that differs so radically from chimpanzees. We are far from a definitive answer, but converging evidence from recent genetic, anatomical, and archaeological studies shows that neural structures, which have an evolutionary history dating back to when dinosaurs roamed the planet, were modified ever so slightly to create the cog­nitive flexibility that makes us human. Apart from our ability to ac­quire a vast store of knowledge, we have a brain that is supremely capable of adapting to change and inducing change. We continually craft patterns of behavior, concepts, and cultures that no one could have predicted.

The archaeological record and genetic evidence suggest that peo­ple who had the same cognitive capabilities as you or me probably lived as far back as as 250,000 years ago. However, we don't live the way our distant ancestors did 50,000 years ago. Nor do we live as our ancestors did in the eighteenth century, or five decades ago. Nor, for that matter, does everyone throughout the world today act in the same manner or share the same values. Unlike ants, frogs, sheep, dogs, monkeys or apes —pick any other species other than Homo sapiens—our actions and thoughts are unpredictable. We are the unpredictable species.

The opposite view, popularized by proponents of what has come be known as "evolutionary psychology," such as Noam Chomsky, Richard Dawkins, Sam Harris, Marc Hauser, and Steven Pinker, is that we are governed by genes that evolved in prehistoric times and.......