A version of this review appeared in Issue 75 of Cosmos Magazine, July 2017
The runaway evolution that drove human brilliance
Darwin’s Unfinished Symphony: How Culture Made the Human Mind
by KEVIN N. LALAND
Princeton University Press (2017)
Evolutionary biologists are often loath to admit the vast gap that exists between our own brilliance and the relatively modest smarts of our animal brethren. Tracing an evolutionary sequence of incremental changes in body shape from apes to humans is reasonably simple. Charting changes in intellect presents more of a challenge. Humans alone have built particle accelerators, propelled astronauts into space, and manipulated the genetic code of other organisms. No other animal even comes close.
In Darwin’s Unfinished Symphony, Kevin Laland not only admits that a seemingly insurmountable gap exists, he takes up the challenge of explaining how a step-wise process of natural selection – as it was first explored by Darwin in his Descent of Man (1871) – can be used to explain what sets the human mind so dramatically apart.
Laland draws on more than two decades of work in his own lab, as well as work by other animal behaviourists and evolutionary biologists, to argue that culture has colluded with genetics to catapult humans far ahead of other animals on the intelligence league board. His elegant theory also positions the human mind as an architect in its own evolution.
Laland traces human intelligence back to its elemental components. Conveniently, many of these components, such as the abilities to imitate, innovate, teach and communicate, have been rigorously interrogated in a staggering array of species, from honeybees to crows, stickleback fish to chimpanzees, dolphins to meerkats.
In recent decades, it has become clear that none of these skills is entirely unique to humans. Chimpanzees use tools to solve puzzles, meerkats teach their young how to kill scorpions, whales bellow out songs in regional dialects. But only in humans do these components come as a package deal. And all promote the evolution of large brains and greater intelligence.
Once our ancestors became reliant on two of these foundational elements – the ability to innovate, and the ability to accurately copy the behaviours of more learned members of our social group – a path towards culture was set. Innovation brought things like stone tools, which became entrenched in our culture thanks to our ability to copy, teach and communicate with each other.
As each of these cognitive skills was honed, more cultural practices were added to our repertoire and retained from one generation to the next. The cultural practices in turn cemented the mental abilities we needed in order for culture to thrive and become more complex. Rather than being a simple outgrowth of human mental abilities, says Laland, culture is part of the explanation for those mental abilities.
Culture also influenced traits not related to our brain. For example, when Northern Europeans began dairy farming, a rare gene variant that allowed adults to digest lactose, the sugar in milk, rapidly spread through the population, and remains common in dairy-consuming cultures today.
This intimate feedback between our genes and our culture created a runaway process, and the speed of human evolution, particularly of the mind, ratcheted up in response. Laland’s account provides a satisfying – if at times laborious – explanation for the origins of intelligence and culture that extends beyond our own existence to that of other animals, our prehistoric forebears, and our hunter-gatherer contemporaries.
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From Nature, March 6, 2019. (Image: Diprotodon skull by AC Sharp, Museum Victoria, downloaded from phenome10k)
