Mother Nature: Natural Selection and the Female of the Species 
by Sarah Blaffer Hrdy.
Chatto, 697 pp., £20, November 1999, 0 7011 6625 8
Show More
Show More

Sarah Hrdy is tough-minded about a tender subject. Motherhood, she says, is a minefield. Mothers love babies passionately – but not unconditionally. We have evolved as adept sociobiologists, able to calculate love. On the other side of the relationship, baby love is unconditional, indeed desperate. Babies want it all, every scrap of attention they can command, at least up to the point where the mother would be so exhausted that her failure would rebound on the baby itself. Babies cannot be physical tyrants, at their body size, so they resort to psychological tyranny: they are irresistible.

In the 700 funny, erudite and combative pages of Mother Nature Hrdy ranges from wet nursing to attachment theory to why a female executive punches through the glass ceiling. Where her biological arguments in general are concerned, I’ll assume, to leap to the bottom line, that the nature/nurture debate has moved by this time from the theoretical sphere to the technological – soon, the feuding over sociobiology is going to seem pretty trivial. As for Hrdy’s political agenda, her robust analysis goes far towards bridging the gulf between biologists and liberal humanists. It turns out that sociobiology has now joined up with feminism to argue for community spirit and cooperative child care. Childcare enabled human mothers to become human.

Mothers’ and babies’ calculations of love reflect the law proposed by the late William Hamilton, a creative genius of sociobiology. (Hamilton died this year of malaria contracted in the Congo, where he was pursuing his latest ideas on the transmission of disease between species – arguably a martyr to his own passion for truth.) Hamilton reasoned that, by genetic logic, kin should help kin when the benefit outweighs the cost, but help is discounted by distance of relationship. A child shares only half her mother’s genes; the other half of the genetic equation comes from the father. The baby is, of course, wholly itself. Hence the potential conflict: the baby wants everything, even if the mother’s interests are different.

But why should a mother hold back, even a little, from anything as wonderful as her child? If evolution is all about die reproduction of genes, surely the child is her hope of a genes, future? Well, not just this child. She needs to spread her devotion over her whole family, to the toddler(s) already born, and also take into account her chances of having another baby after this one. That means saving enough of herself from the needy newborn, so that she can care for the siblings when they have their noses put out of joint by the new arrival.

It means, above all, taking care of herself. Hrdy points out that in human societies as far apart as the !Kung San hunter gatherers of the Kalahari Desert, and the inhabitants of California’s Sacramento Valley, around 40 per cent of women leave no surviving descendants at their death. Our pre-human foremothers probably had an even lower rate of reproductive success. Perhaps only half the females, in an average generation, left grandchildren. Those who became our ancestresses in each generation were lucky, and strong, and able unconsciously to balance their children’s welfare against their own. A mother who squandered the resources needed to maintain her own health would be quickly weeded out – and her family would probably follow her into oblivion.

On top of physical health, it helped a whole lot to be dominant. Relations with males are a crucial part of the story. In the vast majority of primate species, males routinely dominate females. In a few, like our near relations the bonobos, or distant ones like ringtailed lemurs, females are clearly the dominant sex. In some more monogamous species, the sexes are co-dominant. (You must judge for yourselves where humans fall along this continuum.)

What males seek (genetically speaking) revolves around sex – either access to several (or many) females, or control of at least one female’s reproduction to ensure paternity within their own family and a good prospect of siring the next child. (On the kinder side, certainty of paternity often goes with devotion to the child.) Hrdy begins her book by pointing out that males’ attempts to control female reproduction began in prehuman times and show no sign of abating. In a passage that has mysteriously disappeared from the British edition, she tells how the US senator Rick Santorum became near-apoplectic (literally) on the Senate floor while talking about his refusal to let his wife have a late-stage abortion when her life was in danger. (Mrs Santorum survived, although the infant was stillborn.) Congresswoman Patricia Schroeder observed: ‘It’s very interesting the issues they select. They don’t want to intervene in the bodily functions of men.’

Primate females don’t just deal with males, they compete with each other directly over food. Dominant females leave more surviving young on average than subordinate ones. Women, Hrdy argues, still have every incentive to be ambitious – ambition to gain social status is in their genes. This does not mean that every woman is ambitious all the time. No lineage has ever been perpetually dominant, or not for long enough to breed a line of blue-blooded snobs with secure places at the top of the female hierarchy. What has been bred in is the ability to work the social system – knowing how to deal with life as g subordinate, and when ambition will pay off in making a bid for social power. Nowadays, ambition flowers in many spheres: riches or a seat in Parliament, painting pictures or improving society. However, in the not-so-distant past, a sense of personal worth was a sine qua non of successful motherhood.

What about limiting family size? Mammalian females go for quality offspring, more than quantity. If you simply count genes, the bottom line is having great-grandchildren, not how big your immediate family is. Two children who do well enough to raise offspring of their own are a better bet than many children, all of them at risk. The odds have changed, of course, in modern society, but the body’s calculations of how many children it can afford to bear run beneath the calculations of the conscious mind. It often means concentrating all your efforts as a mother on just a few. Whether the limit is imposed by delayed oestrus, sexual abstinence, birth control, spontaneous or induced abortion, or at an extreme, abandoning a baby when there is no hope of raising it, mothers make such choices. We were doing so long before we were human.

So far, all of this applies to most social mammals, including the great apes. Here is one way that humans differ from all other apes, however: we are co-operative breeders. This does not mean group sex, it means that we share childcare. A chimpanzee mother carries her baby and gives it milk for about four years before she comes into oestrus again and bears another. By that time, her older child is feeding itself and runs behind her. An orangutan mother has an eight-year birth interval. Before she has another fuzzy orange-haired moppet, the older sibling can independently rock tall rainforest trees to and fro to make a bridge for itself across the jungle canopy. As Jeanne Altmann pointed out twenty years ago, ‘baboon mothers, like most primate mothers, including humans, are dual-career mothers.’ Still, baboons raise only baboons. Other primates do not try simultaneously to nurse the baby, corral the toddler, help the schoolchild with her homework, and be the breadwinner for the whole family.

When the early feminist Charlotte Perkins Gilman looked at primate motherhood she came to the opposite conclusion from Hrdy. (Gilman is best known for her short story, ‘The Yellow Wallpaper’, about a woman sliding into madness when she is forbidden the chance to write.) In her Women and Economics (1898) Gilman argued that monkey mothers make their own living while carrying a child at the breast. Why, she asked, are women denied that freedom? Hrdy answers that our life history denies it; our children are just too dependent.

A human baby is like an embryo ape. It needs almost a year to achieve the motor control of a newborn chimpanzee. The constraint is our brain. For this to squeeze at birth through a bipedal pelvis, it must be only a quarter of its eventual size. Unlike almost every other mammal, most human brain growth comes after birth, not before. (Kangaroos don’t count.) A neonate with its quarter-grown brain cannot feed or cling or even manage its own temperature control. Most of its repertoire, instead, is self-advertisement.

That is where, according to Hrdy, infant fat comes in. The baby is saying, not just ‘love me’ but ‘keep me.’ Unlike any other primate, it is born with a dimpled roundness which proclaims: ‘I am a healthy baby, a big, bonny baby – invest in me and I will grow even bigger and healtheir.’ A fine pair of lungs, which produce not a mewling wail but the roar that shakes the shopping mall, actually reassures the mother that this child is the one she always wanted. (There is no other theory around to explain why our babies are so plump, except the ‘aquatic ape’ hypothesis championed by Sir Alister Hardy, and, recently, by Elaine Morgan and Simon Bearder. So far, they are a minority of three among physical anthropologists – but I confess it’s a lovely idea that we could have spent a million years on a tropical beach, shedding our fur and tossing our babies into the water to watch them swim.)

Babyhood once over, children and adolescents depend on parental feeding right into their late teens, even in hunter-gatherer societies. Orangutans may stretch to an eight-year birth interval, but if humans waited till the older child was nutritionally independent, we would need a 15-year interval. There had to be a whole new factor in human upbringing, if the species was to survive at all.

The new factor was outside help: help from wherever a mother could find it. From the father, of course, if he is willing – many are indeed supportive and loving. (Hrdy points out, however, that separated fathers in the US are more likely to default on child support than on car payments.) From older siblings – girls in many cultures start baby-minding at six or eight. If possible, from grandmothers. The anthropologist Kristen Hawkes has shown a marked difference in both nutrition and survival among Hadza hunter-gatherer children, depending on whether there is a living grandmother who digs up roots in the dry season. Hrdy adds that ‘we tend not to think of postmenopausal women as having a function’ and that our ‘modern stereotype of grandmothers is more nearly a smiling white-haired old lady bearing Christmas presents than a wiry forager lugging large tubers critical for warding off starvation.’ According to Hawkes’s theory the menopause doesn’t require any special explanation: great apes may cease breeding altogether at about the age of forty, much like ourselves. What does need explaining, however, is how long we live after menopause; nobody else hangs on for twenty years after stopping reproduction. It looks as though women’s old age has been under positive selection. One plus is living long enough to raise your own last child, another comes when you help your daughter – or your daughter-in-law and nieces – with support and childcare and a few dry-season tubers. Unlike the girl child-minder who wants to grow her own body and play her own games, a grandmother gives up little, and gains much, by doting on her grandchildren. In short, as Hrdy says, to raise a human with a human brain takes more than a mother. Other primate mothers may be superb single parents, but we grew out of single parenthood as a preferred strategy around two million years ago.

Do you like this kind of sociobiological story? Or do you cringe? Perhaps you accept it until you turn to the dark side. In Paris in 1780, of 21,000 registered births, only 5 per cent were nursed by their mothers. Most of the rest were sent to the countryside to be wet-nursed by still poorer women. Mortality among babies was so high that wet-nurses were called ‘angelmakers’. Many men inveighed against the practice. In fact, the chosen name of our class of animals – Mammalia – originates in Linnaeus’s campaign for women to nurse their children at their own breasts, at a time when most of his own circle did not do so. Worse, in foundling homes of the past, up to 90 per cent of abandoned children died. The fact that women repeatedly give up their babies to others, often with scant hope for their survival, has led some social historians to question whether mother love itself may be a social construct with no innate basis. Hrdy argues, instead, that maternal instinct is not absolute, but contingent.

Let me go back to basics. Many humanists never sort out the different meanings of the term ‘causation’, which biologists routinely (should) learn when they start to study evolution. One of the founders of ethology, the gentle and visionary Jan Tinbergen, wrote that every action has four separate kinds of cause. There is the proximal cause: in this case, the mother’s poverty, her depression, her fear of society’s disapproval, and the triggering wail in the middle of the night when she is at the end of her tether. There is the developmental cause: the mother is young, and was abused and brought up herself with no model of caring motherhood. There is the phylogenetic cause: she is a human, not a monkey – a monkey mother in most circumstances tries to raise her baby; abandonment of a primate child which is healthy enough to cling onto fur is far less common than among humans, whose babies need so much more physical and social support. Finally, there is the evolutionary function: humans and pre-humans who made the difficult choice to abandon a child when it was really not viable, were more, not less, likely to raise surviving offspring in the end. If contingent motherhood is in our genes, that is because it worked for our foremothers.

A second fallacy among humanists is to think that ‘innate’ means ‘universal’, or simply ‘stereotyped’. Sex itself evolved for the evolutionary benefit of mixing up genes, and producing children different from ourselves. From many points of view, it would be genetically advantageous to just bud off a nice, safe clone, with the genes that we know worked well for ourselves. Instead, we reproduce by sharing half our genes with another person. Every time we have potentially reproductive sex we rejoice in genetic diversity – though humans (and our kin, the bonobos) have extended non-reproductive sex to many other contexts.

Any particular genetic predisposition requires particular external circumstances to bring it to fruition. Mother-love itself reflects external circumstances. In the old days, a severely premature or crippled baby simply could not be raised. Now, it can, to become a person with much to contribute to family and society. In other historic eras, a bastard child might have blighted its mother’s life as well as its own. Now, in much of the Western world, the concept of bastardy is merely quaint – unless it means the mother has no other hope of support. But the fact of contingency is still there. We see it not only in the occasional horror story of a small corpse left in a dumpster, but in every plump, beloved little baby advertising to the world around: ‘I am a keeper.’

The wars over sociobiology have been going on now for a quarter of a century. In her splendid book, Defenders of the Truth,* Ullica Segerstråle compares them to grand opera, with sociobiologists and their opponents singing at full voice from separate balconies, while choruses of their supporters fling up coins of moral capital from below. She ends up, though, blaming the opponents of sociobiology for helping to create a monster called ‘genetic determinism’, and tagging sociobiologists with an all-or-nothing view that nobody holds.

This begins to matter away from the artificially lit stage of the opera. How genes influence behaviour is now the preoccupation of earnest biology undergraduates, who cross inbred strains of mice which are more or less likely to rape, or more or less likely to mother. They trace the relevant genes to their respective points on a chromosome. Eventually, the genes themselves, and their protein products, are unveiled one by one. Cracking the code is no longer the province of the brilliant innovator. A legion of cipher clerks, manual in hand, are reading the secrets of human nature (or at least of inbred mice).

We need to come to terms with this. Crude genetic determinism is (or should be) dead, but genetic influences on behaviour will become common knowledge, and anyone with an interest in ethics, or politics, or social welfare must face that fact. Our conception of ourselves will embrace not only our personal genetic quirks, but the broad sweep of our evolutionary past.

This is where a book like Hrdy’s comes into its own. Much of what it concludes is common sense, even if it’s told here with panache. Any woman who – like Hrdy herself, like me – has juggled children and career will know how we compromised. Hrdy gave up her fieldwork on the sacred monkeys, the hanuman langurs of India, to raise her children. I gave up my Madagascar lemurs for ten years, and went back only when my husband said, ‘Come on, it’s Women’s Year, I’ll take six months to mind the kids.’ We both had the luxury of writing books from home, which turned out to be a smart career choice. Charlotte Perkins Gilman horrified her contemporaries by making the opposite decision. She left her adored daughter behind with her husband and his new wife, reasoning that a stable home would be better for the child than her own life as itinerant author and lecturer. We had choices. A large number of mothers, however, have no choice but to work outside the home, or the family doesn’t eat. That means finding childcare. Arguing the evolutionary background doesn’t change brute facts.

What it does do, however, is give us ammunition. The view that a mother should simply stay at home breeding, whether or not that suits her needs, has long since been consigned to a dustbin called ‘Victoriana’. The more recent view that a woman with children must become a superwoman who does it all, all at once, all by herself, male-style career alongside responsibility for the family, can now be tossed in a dustbin labelled ‘non-human primate’. Childcare by fathers, friends, grandmothers and the community at large, is an integral part of growing up human – the freeing of human mothers to love our babies while still being ourselves.

Send Letters To:

The Editor
London Review of Books,
28 Little Russell Street
London, WC1A 2HN

Please include name, address, and a telephone number.


Vol. 22 No. 17 · 7 September 2000

Alison Jolly’s review of Sarah Blaffer Hrdy’s Mother Nature (LRB, 10 August) suggests that humanists and others in dispute with sociobiologists misunderstand the sophistication of the latters’ reasoning. But their objections are based on rather more than a crude misconception of the nature/nurture dichotomy. Humanists are, in the first place, sceptical of arguments which make indiscriminate forays into the disciplines of history, anthropology and sociology, and which postulate unexamined social assumptions as fact. An example of this is Jolly’s assumption that human nutritional self-sufficiency is achieved around fifteen years of age, whereas an orang-utan becomes independent at eight. In both human and animal species, self-sufficiency can precede puberty and mating by several years. A human eight-year-old is intelligent, clear-sighted, fleet-footed, a good climber and manually dextrous: as fit for life as a hunter-gatherer as for industrial employment or a career as a street urchin. For Jolly to equate human nutritional self-sufficiency with puberty is both to ignore the historical record and to project the social assumptions of our own time onto the functioning of human groups which predate that record and even predate the evolution of language.

Humanists also distrust sociobiologists’ tendency to explain every social and biological phenomenon in terms of genetic advantage. Anthropologists and sociologists abandoned crude functionalist arguments when they realised, decades ago, that an explanation for everything ultimately explains nothing. For example, the capacity of the human female to live for twenty years beyond the menopause poses intriguing questions, but attributing it to the genetic advantage of childminding seems somewhat facile. Other mammalian species, such as wolves, have childminding strategies in which the menopause is not implicated. The issue needs to be examined in the context of studies of group behaviour and hierarchy, and of the relative longevity of species, rather than by reasoning back from the practices of a human community which happen to fit the bill.

Anne Summers
London NW3

Alison Jolly notes that attempts by males to control female reproduction ‘show no sign of abating’. In Australia, the Federal Government proposes to change the Sex Discrimination Act in order to restrict access to in vitro fertilisation not just to heterosexual women, but to married couples. The announcement seemed to come as news to many of the female members of the Government (who of course do not include the Prime Minister or Attorney General), not to mention its (female) Sex Discrimination Commissioner. We need more bonobos in public life.

Gordon Kerry

send letters to

The Editor
London Review of Books
28 Little Russell Street
London, WC1A 2HN

Please include name, address and a telephone number

Read anywhere with the London Review of Books app, available now from the App Store for Apple devices, Google Play for Android devices and Amazon for your Kindle Fire.

Sign up to our newsletter

For highlights from the latest issue, our archive and the blog, as well as news, events and exclusive promotions.

Newsletter Preferences