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6 November 2023

How women were left out of the story of evolution

A radical new history argues that human society was shaped not by hunter-gatherer skills but the bodies of our female ancestors.

By Sophie McBain

Scientists aren’t sure why women tend to outlive men – and yet they do, even though modern medicine was mostly designed for male bodies. Women are less likely to have heart attacks but are more likely to die of them: because women rarely experience classic heart attack symptoms, doctors often misdiagnose them. Even today, most medical trials do not analyse their data for sex differences, and many do not study women at all – and yet we’re learning that women respond differently to many drugs and metabolise painkillers faster. It was only in 1999 that scientists first noticed that women tend to wake up faster from general anaesthetic. For too long science has assumed that women’s bodies are just like men’s, but smaller and with swapped-out reproductive organs. It is only in the past 15 years or so that scientists have begun to appreciate that biological sex differences are much more profound – and more interesting – than that.

As a PhD student studying the evolution of human cognition and narrative, and feeling “flabbergasted” by the male bias in biology, Cat Bohannon read a New York Times article about how women who had liposuction on their bums and thighs were finding that the fat was growing back elsewhere on their body. Some newspaper readers might have enjoyed a sense of Schadenfreude, but Bohannon, as she recalls, was alert to a significant problem not mentioned in the piece. Fat is an organ – or more accurately an organ system – and in women the gluteofemoral fat targeted by lipo is a source of hard-to-make lipids that are essential to nourishing a foetus and newborn. Was anyone thinking about whether having lipo impacts reproductive and infant health? Apparently not. She approached several labs to propose a study analysing whether lipo changes the composition of breast milk, and, while people agreed the study was a good idea, no one took her up on her suggestion.

Eve, Bohannon’s first book, grew out of her fascination with advances in our understanding of female biology, and its wider implications. It is written in the tradition of Caroline Criado Perez’s Invisible Women, which drew popular attention to how much of the world is designed for men, and science books such as Leah Hazard’s Womb and Rachel E Gross’s Vagina Obscura, but with a focus on evolution. Why is the female body built the way it is, Bohannon asks, and how does our evolutionary history – from the emergence of breast milk, wombs and placentas to tools and language – shape the way we live now? Eve is a bold, original and bracingly ambitious feminist retelling of the origin of human society, one that begins with “Morgie” – or Morganucodon, a tiny weasel-like creature that lived among dinosaurs 250 million years ago and may have been the first creature to produce milk – and ends with an exploration of the evolutionary origins of sexism.

Morgie, who is one of several evolutionary forerunners or “Eves” introduced in the book, was able to thrive among giants because she could feed her young with milk that contained not only essential fluids but immunoglobulins and friendly bacteria to protect her fragile newborns from disease. Mammalian milk has co-evolved with bacteria. The sugars in human breast milk are tailored not only to nourish the infant but also its microbiome, helping to cultivate a healthy balance of gut bacteria. Chimps in captivity produce different milk to those in the wild, because they are exposed to different foods and bacteria, and human milk is extraordinarily complex and diverse, reflecting our omnivorous diets and the vast range of pathogens we are exposed to. In this way, breast milk is a social product – it is shaped by the society we live in, and it shapes that society in turn. For instance, maternal stress is known to alter the composition of the mother’s milk in ways that appear to influence infant behaviour in turn. The breastfed child of a stressed mother is more likely to be anxious too, and less trusting of others.

[See also: It’s not too late to save Newsnight]

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In fact, maternal milk may have played a key role in the creation of modern society, Bohannon argues. While many historians believe that cities emerged in response to agriculture, which enabled people to produce the surplus food needed to feed an urban population, she counters that the real driver of urban development may have been wet-nursing.

From the dawn of recorded civilisation, human beings have used women, who were either paid or enslaved, as wet-nurses and this practice may have enabled populations to grow. After all, she reasons, when life expectancy was low and maternal and infant mortality astronomically high, wet-nursing would enable women to give birth more frequently (breastfeeding suppresses fertility, but a wet-nurse can nourish several infants at once). It also would have ensured that babies received the best immunological support to survive childhood illnesses, which spread quickly in urban environments and were extremely dangerous. This is Eve’s most thrilling insight: that women’s bodies may have played a much bigger role in determining the course of history, and the development of civilisation, than we have acknowledged.

In this way, Eve offers an overdue and spirited response to many of the grand theories of mankind published in recent years. For anyone else who has read Jared Diamond’s Guns, Germs and Steel, Yuval Noah Harari’s Sapiens or Michael Muthukrishna’s A Theory of Everyone and wondered why the essential, sustaining work of creating and caring for the next generation is treated like a sideshow, Bohannon offers a refreshing alternative perspective.

What if the foundation of social behaviour wasn’t the desire for dominion over the landscape and over others, but women’s need to collaborate to give birth safely and care for our helpless young? Childbirth is uniquely difficult for humans, because of our small pelvises and big-headed offspring – as Bohannon puts it, “It’s hard to fit a watermelon through a lemon-size hole.” Without medical care, the maternal death rate is 1-2 per cent, and the rate of complications that can harm future fertility is around a third. To improve our odds of surviving as a species, we needed to ensure that more mothers and babies survived birth. Perhaps, Bohannon suggests, it was for this reason that we needed to build stronger bonds, especially between women, and to find ways to communicate and collaborate with each other more closely. Perhaps it was with the arrival of midwifery that we became fully human.

And so she continues. Perhaps the first tool users weren’t male, and the first tools weren’t weapons – wouldn’t women, with their smaller bodies, a baby slung on their hip, have had greater incentive to innovate? Perhaps the first words our forebears uttered were neither “heroic nor grand”: language “probably took shape between two people who already spent most of the time trying to talk to each other: a fussy child who needed to sleep and a mother who needed to sleep even more”. In other words, might mankind have learned to speak the way that humans learn to speak now, by listening to “motherese”, the sing-song, simplified language of a mother speaking to a young child?

Our narratives of human evolution are always partly speculative and ideological, but reading Eve it is hard not to believe that the other stories we tell about our ancestral inheritance – all the fighting and conquering and plundering and pillaging – are missing something fundamental.

Bohannon is also a published poet, and her prose oscillates between lush descriptions of the prehistoric past and a jocular, conversational tone that is sometimes jarringly offhand – she uses the word “rapey” a lot. And you will learn more than you ever knew you wanted to know about “trapdoor” duck vaginas, rhino sex and dog penises.

[See also: The talons of empire]

Approaching contemporary politics from an evolutionary perspective can be enlightening. Bohannon writes that abortion – in the sense of miscarrying for social reasons rather than due to a biological problem – is common in the animal world. Pregnant mice encaged with a male mouse that isn’t the father will frequently miscarry, a phenomenon known as the Bruce effect that has also been observed in horses, lions and some primates. In Sudan, female chimps have been seen to eat plants that are used as an abortifacient by humans, suggesting that they may be using the plants to influence their fertility. Would understanding abortion as something natural help reframe the issue in America?

By the time I reached the concluding chapter of Eve, however, I felt increasingly sceptical of using evolutionary history to draw any normative conclusions about how people should live now. Bohannon argues that sexism is persistent because of its deep evolutionary roots, but that it no longer serves us: sexism makes societies less healthy (through higher rates of STIs and greater maternal mortality); it also makes them poorer (studies show that the best way to boost community wealth is to invest in women and girls) and less intelligent (maternal malnutrition influences a child’s cognitive development). But isn’t it enough to assert that sexism is inherently wrong, and that we’d oppose sexist policies even if they were shown to confer some kind of evolutionary advantage? Bohannon’s feminist revision of evolutionary history feels like an important counterbalance to the male-dominated narratives we tell ourselves about who we are, where we came from and what our purpose is – but one of the advantages of being a big-brained, hard-to-birth being is that we needn’t let our past define us.

Eve: How the Female Body Drove 200 Million Years of Human Evolution
Cat Bohannon
Hutchinson Heinemann, 624pp, £25

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This article appears in the 08 Nov 2023 issue of the New Statesman, The Age of Fury