A key factor in the remarkable evolution of human beings has been the development of our brains and consciousness, which is unique among all species. The price paid for our special intelligence and understanding of the world around us has been difficult birthing and prolonged infancy and childhood, known as neotony, which has allowed babies, infants and children time for extensive learning while they physically grow.
Giving birth can be not only a long and painful process but it can also be deadly. The World Health Organisation estimates that every day about 830 women die of complications around childbirth and, thanks to improvements in care and medicine, that figure is a considerably better than the 1990 data which was around 1200 deaths per day.
The main reason why childbirth is both painful and dangerous is our species, homo sapiens' big head, required for our 'big brains' (https://timboatswain.wixsite.com/website/post/big-brains-and-social-groups). As it is, the baby's head can only just make it down the birth canal which is due to its soft skull bones that are easily moulded to help them squeeze through their mother's birth canal into the world. The process is labelled as 'moulding'. The baby's head is its largest part, so moulding is nature's way of temporarily making it narrower. The problem of the tight width of the birth canal lies in the shape of a woman's pelvis which in turn is a consequence of walking on two legs. Apart from this particular physical problem with childbirth, we all, female and male, pay the price for the evolutionary advantage of walking upright: back problems at some time in our lives and if we are unlucky, varicose veins and haemorrhoids. The evolution of our super-smart brains, with our big heads and walking on two legs, has made birth a dangerous ordeal for both human mother and baby compared to all other mammals.
There is another evolutionary trade-off: our brains and thus our heads are only going to grow bigger after birth so evolution has determined the maximum point in size a baby can be born. Human babies, therefore, in order to squeeze through the mother's narrow birth canal are for all intents and purposes born 'premature' which has meant that their motor skills, for example, limb control, are far behind those of other mammalian species. While babies are developing their amazing mental capacity they are helpless and totally dependent. Baby and infant human beings, therefore, require total care from adults if they are to survive.
The need for being looked after is also mirrored in the elderly when they become frail and their mental health begins to fail. One of the issues the Covid-19 pandemic has highlighted is the high amount of care required by the young and the old, which puts a considerable strain on the resources of society. This vulnerability can be seen as puzzling in the terms of evolutionary logic as, according to Herbert Spencer, evolution is about the 'survival of the fittest'. So why has our evolutionary biology made us, humans, so helpless not only at the beginning but also the end of our lives? And it would seem a paradox that those in their reproductive prime have to spend much of their time caring for the young and the old, so why is this?
New research seems to suggest that the caring of the young and old itself creates an evolutionary advantage in two very important abilities which humans have: that is in learning and cooperating. The argument is that the genetic strength of an individual not only lies in their mature and reproductive period but also across their whole life history – when they are learning and then in their later years by contributing their experience and knowledge of life, 'wisdom', to society.
The human life history of homo sapiens is a stunning one of rapid evolution compared to other great apes: in only 200,000 years (just the blink of an eye in evolutionary terms) we have become the dominant biological force on the planet and unlike most other species, we live long beyond our reproductive capability. If compared to our nearest biological cousins, chimpanzees, on average humans will outlive them by at least 20 years. Whereas infant rearing amongst chimpanzees is done entirely by the mother, in human society childhood is so 'expensive' in time and energy we have pair-bonding between male and female and a history of shared parenting across families and other members of the community (alloparenting).
All young animals seem motivated to experiment and have adventurous curiosity but young humans, because of their extended childhood are quite exceptional in their ability to learn. A prolonged period of childhood then has turned out to be a good long-term survival strategy for our species. Our extended childhood has been made possible by caring adults and their care has enabled human being's extra deep learning, the key to our evolutionary superiority.
It is the caring of children by the non-reproductive elders, not just parents that have provided the care and support that have made it possible for us to develop in the way we have. This care given across the family and society explains the evolutionary importance of post-reproductive humans and why we live so long relatively compared to other primates. Our ancestors relied on the elders for their support, understanding and knowledge of the world. Their knowledge may no longer be so crucial in the age of technology but the support and care given by the older, non-reproductive, members of society played a significant part in the evolutionary development of humans and still plays an important part in the care of the next generation – something we should not forget!
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