For decades the science of child-rearing was guided by patriarchal ideas, but now the cradle rocks to an older rhythm.

The infants had been arranged into neat rows, swaddled in aseptic white cloth the way precision instruments would be secured for shipping. Masked, hooded and gloved nurses cautiously moved down the aisle to record vital functions and administer bottles of formula, closely adhering to the feeding schedule detailed in their log books. To eliminate the possibility of contamination, any handling of their charges was kept to a minimum and parental visits were strictly forbidden. It was a model of efficiency compromised only by the piercing screams of newborns in distress.

American infant wards in the first half of the 20th century were designed around two prevailing ideas, wrote Robert Sapolsky, a Stanford University neuroscientist, in his book Monkeyluv: And Other Essays on Our Lives as Animals (2005): "a worship of sterile, aseptic conditions at all costs, and the belief among the (overwhelmingly male) paediatric establishment that touching, holding, and nurturing infants was sentimental maternal foolishness".

The above is the opening from my new cover article in Times Higher Education out this week (see my last one here) that explores the science of childhood attachment. The piece brings together two overlapping narratives. One strand focuses on the work of primatologist and evolutionary theorist Sarah Blaffer Hrdy and chronicles her personal story of living with the legacy of insecure attachment. The other explores the science that she has spent her career documenting about the evolutionary influences on mothers and offspring, as well as how we can learn from natural history to better provide a secure environment for children today. In addition to Hrdy I interview the evolutionary biologist Robert Trivers, anthropologist Barry Hewlett, and science writer Deborah Blum to show how the science of mother and offspring behavior has challenged many of the assumptions that evolutionary theorists have held for generations.

However, for Hrdy, this research is more than just an academic exercise; it is highly personal as I detail in my article:

"No one ever doubted that my mother loved her five children," Hrdy says, but as a result of her upbringing, "I was a case study in insecure attachment and, except with friends, quite shy." Hrdy would eventually learn to overcome her shyness, but the absence of an emotional bond during her early development left behind a permanent scar: to this day she has no memory of childhood.

In 1990, after Hrdy's brother died tragically at the age of 30, she received his baby book from their early childhood in Houston.

"I was amazed by how much detailed information there was in it," she says. Having only vague impressions of their distant caregivers, Hrdy couldn't imagine that one of them had kept such a complete record.

"But then I looked more closely and I realised that it was my handwriting," she says. "I was keeping all of these detailed notes on my brother's development, but I have no recollection of caring for him."

The precise mechanism for such childhood memory loss continues to be debated by psychologists, but the common experiences of adults who share this kind of amnesia form a consistent pattern. Like those children who suffered the effects of hospitalism in the early part of the 20th century, the absence of childhood attachment with a caregiver results in physiological changes that have potentially lifelong consequences.

The early pioneers in the science of childhood attachment were the psychologists John Bowlby and Harry Harlow whose research laid the foundation for a field change among their colleagues. Up until the 1950s the school of thought known as behaviorism was all but universally accepted among psychologists. This school held that everything that animals do--including mental traits--should be understood as behaviors. By changing the behaviors it was thought you could change how individuals think or even feel. However, by putting these assumptions to the test they were demonstrated to be woefully inadequate, as I show through the experiments done on primate infants.

At the same time that Bowlby was developing his evolutionary theory of attachment in the mid-1950s, a hard-drinking, chain-smoking workaholic by the name of Harry Harlow was busy creating separation anxiety in the lab. While his original intention was to discover the cheapest way to breed monkeys for experimentation, Harlow ended up providing empirical evidence to refute those psychologists who advocated a cold, emotionless approach to parenting by creating the kind of wiry caregiver that they described, quite literally.

By placing a baby monkey into a cage with two artificial "surrogate" mothers - one made of soft terrycloth and the other a patchwork of wire mesh - Harlow sought to test the behaviourists' assumption that an infant was motivated only by a parent who provided them with nourishment. In the course of the experiment, eight identical cages would be established, but with one important variation: in four of them, only the "wire mom" would be equipped with a bottle, while in the other half only the "cloth mom" would be. If the behaviourists were correct, the infant should prefer whichever "mother" was the source of food.

The results were unambiguous: in both cases infants spent nearly all of their time clinging to their cloth mother regardless of whether or not it was the one with the bottle. In the cages where wire mom was so equipped, the infants would leave soft mom's embrace to feed, only to immediately return for the "contact comfort" they obviously required.

"The effects were so strong", wrote Deborah Blum, the Pulitzer prizewinning journalist who chronicled Harlow's experiment in her book Love at Goon Park: Harry Harlow and the Science of Affection (2002), "that the scientists began to wonder about other ways to test that bond and the security that seemed to come with it."

Harlow next placed each infant - along with both surrogate mothers - into a 6 sq ft playspace that the monkeys could explore independently. When cloth mom was present, the infants would each hesitantly wander around their novel environment, confident that they could return to the safety of their surrogate's embrace if they needed to. But in those trials where Harlow had cloth mom removed, the infants would huddle in the corner screeching, sucking their hands or rocking back and forth repeatedly. Even those infants who were used to feeding from wire mom had a similar response: she was no better than the strange objects that surrounded her.

Subsequent experiments, this time with flesh-and-blood mothers, found that only those infants who had first established a secure attachment could successfully forge relationships with other members of their group. Without this, infants would experience heightened anxiety in social situations, just as Bowlby described for children with insecure attachment.

It is from this foundation that the science of childhood attachment gets truly interesting and, as Hrdy and Trivers go on to explain, inverts the perspective that evolutionary biologists have held dating back to the Victorian era.

The uniting of behavioural and genomic evidence, something that Hrdy and Trivers have independently explored throughout their careers, has revolutionised the way that mothers and children are viewed from the perspective of natural history. And rather than an evolutionary logic that places men at the top of the hierarchy, followed by women and children at lower levels, the perspective has now been inverted.

"Instead of the classical, so-called 'patriarchal' society," Trivers says, "the logic goes the other way around: children; women as primary investors; lastly and hardest to justify, males."

Thanks for reading and I will do my best to answer any questions you may have in the comments below.