Consider the aorta: our body’s largest artery stiffens and slackens with age, like overstretched elastic, and can bulge out forming an aneurysm that’s prone to rupture. Aortic aneurysms occur six times more often in men than women. But if a woman does have one, it’s more likely to burst, she’s less likely to get effective treatment and more likely to die. These outcomes are a tangle of sex (influenced by chromosomes, physiology and hormones) and gender (how we identify, behave in our environment and interact with one another). Why is our society calibrated for men so that women receive substandard medical care? And why are researchers not studying half the world’s population who are excellent at not getting aneurysms?
Eve is interested in the origins of such questions, plumbing the depths of what’s different – for better and for worse – about the female body. This long overdue evolutionary account is the pre-history to Caroline Criado Perez’s Invisible Women (2019), showing how wrong it is to think of women as just men with breasts and wombs bolted on. Over hundreds of thousands of years, women have developed more sensitive noses (particularly around ovulation and pregnancy), finer hearing at high frequencies, extended colour vision, and longer life expectancy than men by an impressive half decade. Forget plasma exchange and supplementation – entrepreneurs trying to extend human life should be studying women, who comprise around 80% of today’s centenarians.
American academic and author Cat Bohannon asks how this came to be, tracing defining female features back to our “presumed true ancestors”, our Eves as she calls them. The story starts more than 200m years ago in the Jurassic period with a rodent, Morganucodon, nicknamed Morgie, which still laid eggs but also had glands on its tummy that began secreting milk. It was perhaps the first breastfeeder. We then meet Protungulatum donnae, a squirrelish creature, which initiated placental pregnancy. This was a high-risk hack. As Homo habilis’ heads expanded, the female pelvis unfortunately did not. Our forebears’ survival relied less on fire, farming and the wheel than on reproductive choice, gynaecology and midwifery. Pregnancy is a perilous stress test on a mother’s organs and a struggle between maternal and infant needs, though “you don’t want the foetus to win or lose the war, because either way can kill you”. Assisting other women in labour was revolutionary, given the intense trust and collaboration that was required.
Bohannon calls on her astounding disciplinary range to tell this epic tale. Her writing ripples with references from literature, film studies, biochemistry, cognitive science and anthropology. No wonder it took her 10 years to finish. The footnotes alone, which are particularly learned, irreverent and funny, are a masterpiece. Bohannon isn’t short on ideas that will anger some readers. She is bold when speaking against abortion restrictions, the gender wage gap, sex essentialism (“it’s clear that trans women are women”) and chastity laws. There’s also a grungy lushness to her prose that celebrates saliva, cervical and laryngeal mucus, buttocks, the “metal tang of old menstrual blood”, and fat. Her shame-free voice bears the signature of someone who has explored, tested and loved her own body and mind, as a life drawing model, poet, egg donor, academic, musician and very nearly a sex worker.
Evolution, as Bohannon emphasises, doesn’t care about our contemporary preferences or sensitivities. This emboldens her to confront uncomfortable stereotypes, like whether women’s brains have evolved to be inferior to men’s (in fact, the sexes have strikingly similar cerebral equipment). She then wonders whether men evolved to rape. Among species such as mallards where rape is common, the male duck’s “corkscrew” penis forces entry while the female’s “long, winding vagina will close off, trapping unwanted sperm in a side tunnel”. Man’s “straightforward” genitalia by comparison suggests we evolved for consensual sex. But what if Bohannon had found the opposite to be true about our evolutionary inheritance? Sexual assault is abhorrent, and an argument rooted in ideas of “naturalness” should never trump our moral code. Eve reveals the limitations of evolutionary reasoning, exposing that our present doesn’t make sense without thinking about differences of gender as well as of sex. A modern woman’s brain is not constructed from genetic instructions alone, untouched by the world in which she lives: “It takes a whole girlhood in a sexist environment to build a brain like that.”
There is no fossil record of brains or wombs. Where any organ once was becomes a cavity of uncertainty. Bohannon finds the gaps “incredibly fun”, excavating possibilities from silence. She revises the opening of Stanley Kubrick’s 2001: A Space Odyssey, for example, replacing the testosterone-filled scene of early man as the “primordial inventor” of weapons, with women who were sharpening the tools while also making the babies. To read Eve as a factual record of the deep past would be misleading and, frankly, misses the point of Bohannon’s achievement. It’s an informed reimagining. After all, the book’s mixture of science and speculation is more accurate than the illusion of a sex-neutral body that medicine has been peddling for centuries.
The author’s parting plea is that we learn more about women and girls. In the UK, unlike the US, there is still no regulation that insists women are included in medical research. Not everyone agrees with the ethical good of extending participation. Might they acknowledge that being specific about people’s sex and gender leads to more rigorous and reproducible scientific results? It’s also a safer approach. Studying men, unaffected by periods and pregnancy, may produce “clean” data, but only by shifting risk for women out of the controlled setting of a lab and into the chaos of the real world. For the remaining male naysayers, researching sex and gender differences is ultimately selfish too. Every human brain and body has gestated in a female frame. The more we know about women, from their ovaries to their aortas, the more we know about everybody, which may invite us all to think of ourselves in radically new ways.
Kate Womersley is a doctor and academic specialising in psychiatry. Her work at Imperial College London focuses on sex and gender equity in biomedical research
• Eve: How The Female Body Drove 200 Million Years of Human Evolution by Cat Bohannon is published by Hutchinson Heinemann (£25). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply
