If there’s one thing we can say with certainty about the history of sleep, it’s that our ancestors didn’t sleep like we do today.

So, how did they sleep? We are beginning to find some answers, studying modern hunter–gatherer cultures to gain some insight into how our early ancestors slept.

As a civilisation, we’re at a crossroads. Across the world, we’re digging deep into the biological factors that make us who we are, why we behave the way we do, the basic instincts that make up our framework and provide answers to essential questions about Homo sapiens. In this exploration, scientists and researchers are finding that the mysterious trail back to our origins is peppered with traditional wisdom.

Studies of cultural practices that our ancestors followed have revealed an instinctive approach to everything for survival. In modern times, however, this wisdom that came to us biologically, like an impulse, has been forced to retreat to the shadows for the sake of convenience as we have forged a path to economic growth. Along the way, we have dispensed with some of those impulses that have protected us for centuries.

Experts are now pausing to reflect on what we’ve left behind. Even as we chant the various mantras of good living – “eat what your grandmother ate”, “grow your own food”, “slow down”, “listen to your body”, “ditch the artificial for the natural”, etc – let’s understand how best to sleep naturally, biologically, harmoniously. To do that, let’s go back to the beginning, to when humans slept in the wild.

In 2014, an experiment to investigate how people slept in prehistoric living conditions proved insightful. The researchers found that in the absence of modern living conditions – such as screens and artificial light, and stressful, busy routines – the subjects of the study went to sleep earlier and slept longer. These are the conditions that children too sleep best in.

More importantly, as several other findings have shown, early tribes shared common sleeping space, children attached to their parents, and families wrapped up work by sunset and woke up at sunrise. Leaving babies in separate spaces, away from their caregivers, day or night, was simply not a consideration. Babies fed and slept according to their biological needs and thrived when attached firmly to their caregivers. Those who weren’t, didn’t survive, and were eaten up by wild animals.

Bestselling author and paediatrician Carlos González in the excellent parenting bible Kiss Me: How to Raise Your Children with Love writes,

Mothers who left their children alone for more than a few minutes soon had no children. Their genes were eliminated by natural selection. By contrast, the genes that compelled mothers to stay with their children were passed down to numerous descendants. You are one of those descendants. Modern women have a natural genetic inclination to stay with their children...

In the book, González explains the simple truth behind why children sleep better when they are close to their caregivers and why they resist sleeping alone.

A series of studies led by Darcia Narvaez, professor of Psychology at the University of Notre Dame, went a step further to examine the effects of such an arrangement. It was concluded that child-rearing practices in foraging hunter-gatherer societies – like holding, sleeping close to adult caregivers, responding to children every time they cried and so on – led to “better mental health, greater empathy and conscience development, and higher intelligence in children”.

In modern societies, she found, “an increased level of aggression, anxiety and depression is linked with depriving children of empathy and compassion in the early years”.

In modern life, parents are under tremendous pressure to teach their children to become less dependent on them and sleep independently, without needing a feed from the breast and without physical closeness. In ancient times, this wasn’t a logical expectation at all because it was deeply linked to survival.

So, you might be correct to think that we are putting unrealistic expectations on ourselves and our children when we expect them to sleep on their own, on a separate sleeping surface such as a cot, before they can utter their first word and fend for themselves in most other ways.

The truth is, our ancestors knew exactly how to sleep. It wasn’t considered something anyone had to “learn”. Babies know how to sleep right from the time they are in the womb, where they sleep 80-90 per cent of the time. In there, they have all the right conditions for a cosy sleep – a warm, dark space to nestle in where they instinctively feel safe and secure, their mother and father’s muffled voices drifting in and out of their consciousness, music and lyrics to their ears.

So, when babies come out into the world, wailing and red-faced, they expect the same conditions, which can be somewhat replicated in the warm safety of their parents’ arms, while suckling on-demand at the mother’s breast and while snoozing softly on a loving caregiver’s lap. As González writes in Kiss Me:

The greater the divide between the way we want our children to sleep and the way that comes naturally to them, the more we will need to teach them how to sleep. It is much easier to teach them to sleep in pyjamas or in a bed than it is to teach them to sleep without their mother.

So, you see, when many parents wonder why children don’t like being left alone, especially when they’re drifting to sleep, the answer lies in the history of humankind and how we are essentially wired.

Our basic instincts are built to crave physical closeness and community life. This is why babies cry when they are left alone – they fear for their lives. Many parents misunderstand crying to be a sign of manipulation. But babies are not capable of manipulation. They are not trying to make life difficult for you.

They are only trying to survive, and crying is the only way they know to get your attention to express to you something they don’t yet quite have the words for. When they cry, it’s to express that they are insecure, or hungry, or need a nappy change. By all accounts, they just need your attention.

During our engagements with the parenting community over the years, we found that it is this anthropological discourse – to understand where babies’ needs arise from – that is missing. It is particularly lacking in medical professionals who work with children, such as paediatricians, who are often not well-versed in gentle parenting methods and the biological impulses of babies.

There are, of course, exceptions, and we have also encountered the odd paediatrician who recommends natural parenting methods and age-appropriate sleep. But it’s rare. The paediatric community’s recommendations, particularly in Western cultures, is that children should be trained to sleep separately and should be weaned from night feeds at 6-9 months old. It is now being widely countered by leading experts across the world.

One of them is Dr James McKenna, recognised as a leading authority on the subject of mother–infant co-sleeping in relation to breastfeeding and sudden infant death syndrome (SIDS). In his groundbreaking Mother-Baby Behavioural Sleep Laboratory, at the University of Notre Dame, Indiana, he studied through an anthropological lens how sleeping environments reflect and respond to family needs – in particular, how they affect mothers, breastfeeding and infants’ physiological and psychological well- being and development.

In his paper, “Mother-Infant Cosleeping with Breastfeeding in the Western Industrialised Context: A Bio-Cultural Perspective”, he observes:

First, be aware that only in the last century have humans anywhere asked where their babies should or would sleep. It is a very “modern” question not asked by the majority of contemporary people. Indeed, perhaps it is more pertinent to ask whether billions of people could be wrong? The overwhelming majority of contemporary parents outside the western industrialised world appreciate and accept without question the benefits and necessity, if not the inevitability, of mothers sleeping next to their infants (cosleeping), which is seen as natural and expected, if not morally appropriate.

It is expected that a caregiver will be sleeping next to an infant because babies can’t (no one can, really) sleep deeply and restoratively till they feel secure and comforted. This is why the moment you pick your baby up, he/she feels taken care of, and after being nursed or rocked or walked and held close to you, drops right off to sleep.

Sleeping Like a Baby Himani Dalmia, Neha Bhatt

Excerpted with permission from Sleeping Like a Baby, Himani Dalmia and Neha Bhatt, Penguin Books.