BOOK REVIEW

The rise of the greedy-brained ape

Gaia Vince takes an enjoyable sprint through human evolution — Tim Radford reviews.
Tim Radford is a former science editor of The Guardian. His book The Consolations of Physics is published by Sceptre.
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Shilluk tribes people gather in a circle under a large tree for traditional storytelling

Shilluk people in Sudan gather in the shade for traditional storytelling.Credit: Eye Ubiquitous/Alamy

Transcendence: How Humans Evolved through Fire, Language, Beauty, and Time Gaia Vince Allen Lane (2019)

Gaze into a mirror. Reflected is a marvel of evolution: a weak-jawed, bipedal omnivore with a greedy brain, in which 100 billion neurons consume 20% of the body’s energy intake. Science journalist Gaia Vince urges us towards such reflections in Transcendence, a book tracing the journey of Homo sapiens through genes, environment and culture to what might be, she surmises, a new state of being.

For her hugely enjoyable sprint through human evolutionary history, Vince (erstwhile news editor of this journal) intertwines many threads: language and writing; the command of tools, pursuit of beauty and appetite for trinkets; and the urge to build things, awareness of time and pursuit of reason. She tracks the cultural explosion, triggered by technological discovery, that gathered pace with the first trade in obsidian blades in East Africa at least 320,000 years ago. That has climaxed this century with the capacity to exploit 40% of the planet’s total primary production.

How did we do it? Vince examines, for instance, our access to and use of energy. Other primates must chew for five hours a day to survive. Humans do so for no more than an hour. We are active 16 hours a day, a tranche during which other mammals sleep. We learn by blind variation and selective retention. Vince proposes that our ancestors enhanced that process of learning from each other with the command of fire: it is 10 times more efficient to eat cooked meat than raw, and heat releases 50% of all the carbohydrates in cereals and tubers.

Thus Homo sapiens secured survival and achieved dominance by exploiting extra energy. The roughly 2,000 calories ideally consumed by one human each day generates about 90 watts: enough energy for one incandescent light bulb. At the flick of a switch or turn of a key, the average human now has access to roughly 2,300 watts of energy from the hardware that powers our lives — and the richest have much more.

Humans are more social than other primates. We can keep track of around 150 other people, which demands a large brain and might also help to expand it. To learn a fact stimulates one part of the brain; to hear a story activates many. That is why we find information 22 times more memorable in narrative form. Homo sapiens is a storytelling animal, and this adaptation ensures the transmission of skills and knowledge as fable, epic or cautionary tale. Vince, drawing on brain-scan studies, shows that neuroscientists have noted a synchrony, both spatial and temporal, between speaker and listener during storytelling, a phenomenon known as ‘neural coupling’.

The human capacity for narrative, metaphor and pattern-matching can lead us to see meaning where there is none, however. In a US psychological experiment in 1944, students were shown a short animation of two triangles and a circle passing across a screen, while a rectangle remained stationary (F. Heider & M. Simnel Am. J. Psychol. 57, 243–259; 1944). Of the subjects, 33 out of 34 anthropomorphized the moving shapes, creating narratives of anxiety, concern, rage and frustration.

Vince continually returns to the evolutionary triad of genetics, environment and culture to address our similarities and differences. Some human biological adaptations are part of cultural variety. The semi-nomadic Moken people of Thailand can see clearly underwater because they can constrict their pupils to the maximum limit of human capacity, increasing depth of field and changing the lens shape. This is a learnt capacity: in an experiment, Swedish children mastered it. Divers of the Bajau people in Indonesia, however, exemplify heritability and environmental selection at work. Their spleens are 50% larger than average, acting as a reservoir of oxygenated blood and endowing them with consummate endurance underwater.

Our most profound cultural tool, language, is in some ways culturally selected. We owe our acrobatic way with words to a larynx that descends at three months of age. Thereafter, Vince notes, we can no longer swallow and breathe at the same time. Our languages shape our thinking and cultural identity in many ways, but environment also shapes speech. Languages in warm, wet, wooded regions tend to have more vowels and fewer consonants. Languages that emerged at altitude have more words with a strong expulsion of air in the consonants.

Tonality in languages (in which a word has different tones that change meaning) is important. The emergence of non-tonal languages over the past 50,000 years — Homer’s Greek was tonal, modern Greek is not — might have influenced the spread of two gene variants involved in brain growth, according to a 2007 study (D. Dediu and D. R. Ladd Proc. Natl Acad. Sci. USA 104, 10944–10949; 2007). So words also shape our inheritance.

Vince has a lot to say about words. The average response rate between speakers during a conversation is 200 milliseconds. But it takes 600 milliseconds for the signal to go from ears to brain, to understanding, to the preparation of a response and its transmission. Thus, conversation must rely on a sophisticated prediction system that commits a large part of the brain to both speaking and listening. Language, writes Vince, “gives us an unparalleled ability to convey an infinity of ideas. We use it mainly to talk about ourselves.”

Of course we do. Humans might not be so much Homo sapiens as Homo narcissus, the self-absorbed species. Yet all of our capacities together have, in their different ways, endowed us with the capacity to become a super-organism. We are now a globally connected urban species, outsourcing our brains to computers, increasingly to artificial intelligence and (so far) to nine billion robots. We have begun the Anthropocene, and our demands on the planet are not sustainable. That could usher in a new dark age, or a global order in a new shared civilization. We transcend our evolutionary beginnings.

Vince dubs this emerging species Homo omnis, or Homni for short. Her chosen analogue for such a biological super-organism is not flattering: it is the slime mould, in which single cells coalesce as one to move on. The fortunate are protected at the centre; those on the margin become vulnerable to environmental change. Which sounds disturbingly like us.

Many aspects of Transcendence have been explored before. And, with that wealth of palaeoanthropological and other research to draw from, most of the chapters become a mosaic of tersely introduced evidence. Read it anyway. It is at least 22 times more memorable than many textbooks, and a good story without — so far — a happy ending.

Nature 574, 623-625 (2019)

doi: 10.1038/d41586-019-03084-4

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