Murderous side of maternal instincts

Most popular sociobiology deals with the sexual sparring of grown men and women: infants, though acknowledged as the ultimate objective, do not figure highly in such works. Perhaps the consumers of sociobiology are those in an uncommitted stage who will graduate to more sober reading when they settle down to rear offspring.

Beyond the fact of their unreliability, men do not feature greatly in Mother Nature : this is a book about mothers and infants. Its author, primatologist Sarah Blaffer Hrdy, made her name in the 1970s documenting infanticide by male langur monkeys. She also provided its first functional explanation as an attempt by an incoming male to bring infant-burdened females immediately into oestrous and so increase his reproductive opportunities. The astonishing collusion that females may show in the extermination of their own infants makes sociobiological sense: the infant will be killed eventually by the male and if killed sooner rather than later the female can get on with conceiving another.

None of this went down very well in a scientific era in which behaviour was still erroneously believed to serve the survival of the species. Nor, 30 years later, will Mother Nature be welcomed by the admirers of "the maternal instinct".

Hrdy's champion is George Eliot, a Darwinist of sorts but also a feminist and satirist, and one who suffered an extraordinary and humiliating rejection from Herbert "survival of the fittest" Spencer on the grounds that her insufficient femininity would compromise their mutual genetic lineage. Eliot and her contemporaries mocked the Victorian Darwinists' marginalisation of the females' role in evolution and their relegation to the status of brood bearers. Indeed, the sexual emancipation of the following century revealed that women were perfectly capable of disregarding their supposed instinct for mothering, and Darwinism was rejected by many as a reactionary doctrine. The feminists were wrong to reject Darwinism, but they were right to reject its ill-considered Victorian relic of unconditional motherly love. In Mother Nature , Hrdy examines this concept, stripping away the parts of cultural conditioning and patriarchal fantasy to reveal maternal instincts that are real but disquietingly contingent.

The facts of mothering are these: it takes up to 13 million calories of investment to rear a child to self-sufficiency, and there can be no certainty of help from the father. The ethnographic record for numerous pre-technological societies shows that infanticide is considered the best option for a mother who knows that her child will not survive and who may jeopardise the mother's own survival. Nor is this suspension of the maternal instinct limited to supposed savages. For the past millennium, Europeans under legal and religious constraints preventing them from killing their children have still opted to abandon them whenever opportunities arose. By 1640, 20 per cent of baptised babies in France were being left at state orphanages. Anonymity in this and other depositaries was preserved by ringing a bell and placing the baby in a rotating barrel in the wall, to be received on the other side. In lean times, grills had to be placed across the opening to prevent older children being shoved in as well. Whenever philanthropists opened orphanages, they were immediately flooded. It seems that women's desire to abandon their children has always been underestimated.

Infanticide is rare in our primate cousins. Why gestate a child only to abandon it? Hrdy argues that the problem arises with the long childhood that evolved around the time of Homo erectus , which resulted in mothers having to provide for multiple offspring of differing ages, on fluctuating resources. Her "grandmother's clock hypothesis" is that general selection in humans for longevity meant lengthened childhoods, which were facilitated by a post-menopausal period in which grandmothers cared for their descendants. In contrast to received wisdom, Hrdy claims no special adaptiveness of extended childhood, rather that it is a consequence of the invariant rules of life history strategies. They would have to be fiercely invariant to allow for the burden of extended childhood if it really does confer no advantage, grandmother provisioning or no.

What is both convincing and thought provoking, however, is Hrdy's observation that once humans evolved into a niche in which mothers were selected to abandon babies, babies themselves would be selected to resist abandonment. Assuming that mothers abandon when offspring prospects are low, it behooves the infant to look like a good investment. This is why infants are so fat, Hrdy argues - they need to come out looking like survivors. The placenta, a parasitic organ, directs maternal resources to the foetus in spite of the mother, so the baby can call the shots in this even if it makes labour painful and dangerous for the mother.

This opens a surprising door into developmental psychology. In the 1960s and 1970s, John Bowlby revolutionised this field by putting mother-infant attachment in the context of evolutionary adaptiveness. He envisaged the child's attachment to the mother to be based on the perils of predators and the like. Hrdy's "modest addendum" is that what the Pleistocene infant really dreaded was not a hungry hyena, but a much more likely threat - the possibility of abandonment. Nor need this have been an all-or-nothing thing. Infanticide lies at one end of a continuum of maternal retrenchment,psychological withdrawal and denial of resources. Children feel the pinch at every step. A 21st-century infant, unaware that it is protected by law, is extremely sensitive to the "whiff of maternal ambivalence". Psychoanalysis thus failed children by relegating morbid thoughts of abandonment to the realm of fantasy. Perhaps the greatest value of Hrdy's iconoclastic review of the mother-infant bond will be to give the infant's fears due weight in its future psychological functioning.

There is more food for thought in Mother Nature than I can relate here, including discussions of gene imprinting, a theory of changeling myths and some unpalatable reflections on what really happens in some cases of sudden infant death. The book is anthropology as it should be - the study of humans as the product of biology and history. I recommend it to all mothers and newborns.

Thomas Sambrook is teaching fellow in psychology, University of Stirling.