by Anna Machin
In contrast, human apes have evolved a very different model of fathering, where dads stick around to help out with their children. How they achieve this varies widely between cultures, something that we will explore later in this book, but at the end of the day they all play a critical role in their children’s lives. And the need for their involvement began with the unique combination of the two anatomical features – bipedalism and big brains – I mentioned earlier. For, if you are a quadruped – that is, you walk on four legs – your legs are arranged rather like the legs of a table, each at a considerable distance from the other, at the corners of your body. In contrast, the legs of a biped are close together, meaning that we have a much deeper and narrower pelvis and, as a result, birth canal than our four-legged friends. In itself, this narrowing of the birth canal is not an issue, but combine it with a large brain and you quickly hit a problem.
In terms of development, animal babies can emerge from the womb behaving in one of two ways: either very advanced, with eyes and ears open, fur or hair developed and ready to move around independently soon after birth; or helpless, unable to move, with eyes and ears closed. The first category of development is called precocial – from which we get the word ‘precocious’ – and it is the usual state of affairs for ape babies. It still astounds me how adeptly a chimp baby can climb unaided through the trees only a few days after birth. The second category is labelled altricial, and you will recognize it as the experience of puppies and kittens. These two paths of growth exist because, in the vast majority of species, the growth of the baby’s brain happens at one of two times: either in the womb – the chimp model – or after birth, as happens in puppies and kittens. I say the vast majority of species because there is one exception. Us.
Human brains are significantly larger than would be expected for a mammal of our body weight – nearly six times larger, in fact. And it is this anatomical attribute that has enabled us to be so successful. We have developed language, exhibited an unsurpassed ability to innovate and are capable of commanding a level of control over our environment that has enabled us to dominate the earth. But because we have such unusually large brains for our body size, we need longer for our brains to grow. And herein lies the problem. Our narrowed pelvis means that this crucial period of development cannot occur in the womb because it would be impossible for the baby to travel successfully through our narrowed birth canal – indeed, both the mother and baby would be at significant risk of death. So, to ensure the survival of the species, evolution has selected for humans to have an unusually short gestation length, meaning that human babies are born before they are fully developed. This results in two outcomes: one, that human babies display a combination of characteristics at birth – the helplessness of a puppy but the open eyes and ears of a chimp; and two, that humans are the only species that exhibits a period of significant brain growth both before and after birth. Problem solved.
But is it? Allowing a period of significant brain growth after birth, one year in our case, allows the brain to reach its full potential, but it does mean that the mother has a considerable burden to deal with; a very dependent, immobile, energy-hungry baby. Not only must she expend considerable energy carrying her offspring but, theoretically, she should also have to breastfeed it for longer than would be the case if her baby’s period of brain growth occurred only before birth, as occurs in chimps. But, in reality, this is not the case. While in some societies human mothers will breastfeed beyond six months, it is wholly possible, and the norm within the West, to wean a baby onto solid food when it reaches this age. Why do humans display such a short period of lactation?
It is all down to demographics and the survival of the species. The evolution of the shortened periods of gestation and lactation probably evolved around the same time, 1.8 million years ago with the evolution of Homo ergaster. Solely breastfeeding prevents a mother becoming pregnant again, evolution’s way of making sure all her time and energy is committed to the needs of her growing baby. But if our ancestors had been committed to doing this to the extent required by the post-birth development of the human brain – the most energy-hungry organ in our body, even when it’s not growing – it would have meant that the time between human births was so long that the species was unable to replace itself. Our ancestors would have become extinct and maybe another species would have come to dominate the earth. But by reducing the amount of time that they breastfeed, mothers could stop feeding their children earlier, become fertile again and ensure that they were producing babies at a rate sufficient to maintain, and indeed enlarge, the population.
Any parent can relate to the overwhelmed feeling engendered by trying to juggle the needs of a newborn baby with the incessant demands of a toddler to be fed, cuddled, comforted and played with. I remember the stress involved in trying to breastfeed my second child while struggling to locate the right Teletubbies DVD and produce a drink and snack for my firstborn. You become very adept at doing everything one-handed. But imagine this with all the advantages that modern life has bestowed upon us removed – no labour-saving devices, baby equipment and family-planning methods. This was the lot of the prehistoric female Homo ergaster. Without the capacity to control her own reproduction from the age of sexual maturity, around eleven to thirteen years of age, she would be constantly either pregnant or breastfeeding a newborn and trying to deal with any number of dependent toddlers. Not for her the leisurely five-year period between births common in the chimpanzee.
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Humans are defined by the extraordinary extent of our cooperation. Think how many times a day you interact with a fellow human to achieve a goal. We cooperate to find or produce the food and water resources that are vital for our survival, to teach and learn the skills and knowledge to live and be successful, to trade, and to raise our children. One of the most powerful forms of cooperation is that between genetic relatives, or kin. This is known as kin selection, and it relies on the fact that by helping those to whom we are blood-related we are benefiting our own survival. In the main, this is not because by helping our kin we can expect help in return when we need it, although this is often the case, but because we share genes and, as any good evolutionary biologist knows, the survival of these genes is ultimately all that matters. This is the concept of the ‘selfish gene’, first labelled and explored by Richard Dawkins in his 1976 book of the same name, and it proposes that the unit o f inheritance on which evolution acts is not the individual but the gene. So, by helping a relative care for their children we ensure the survival of those children and, by association, versions of our own genes. It goes without saying that the closer the relative is to you in blood terms, the more advantageous it is for you to help them with their children, as the number of genes you share with them is greater. Hence it is nearly universally the case that grandparents are the most likely to care for grandchildren after the children’s own parents.
So, it is to her kin that our female Homo ergaster would have turned in her hour of need. Whether it was, in fact, her mother is debatable, as it is unclear if the lifespan of our ancestors was sufficient to allow anyone to reach the ripe old age of grandparenthood. Despite millennia of evolution, the age of menopause has always been around fifty years of age and the frequency of skeletons of this age in the fossil record is notably low, if not non-existent (arguing over this point fills many happy hours for anthropologists – we are a strange breed). But we know that it would have been some form of female kin. How do we know this? Because evolution is parsimonious, that is, it will always achieve its end point by the least complicated and/or least expensive route. In all cases, it is energetically less costly to cooperate with someone of the same sex than someone of the opposite sex. I think we can all relate to this. This is because by cooperating with someone of the same sex, you are using the same currency of exchange, making acts of cooperation easy to follow. Even among kin, cooperation is expected to be more or less reciprocal – you scratch my back and I will scratch yours – so k
eeping track of the acts of cooperation is essential to make sure that you are not always the one offering help. And the easier it is to do this, the less brain power is involved and the less precious energy is consumed. In the evolutionary past, when it came to children, women exchanged the same types of act, namely those associated with the care or protection of the child. For men, the reasons were different – they might help with a child because they hoped it would increase their chances of being mum’s next partner, a very different form of currency. This made the exchange rate between the two forms of currency incredibly complicated to calculate, so evolution decreed that we avoided having to make these exchanges unless we absolutely had to. As a consequence, mothers sought out other women to help them in the first instance.
So, there our female Homo ergaster was, raising her children with the help of her female relatives; her sisters, cousins and even elder daughters. As we know, for over a million years such help sufficed, but around 500,000 years ago, with the second large increase in brain size, the energetic costs of raising an infant again became too much to cope with. This huge leap in brain size, to close to the 1,300 cubic centimetres of today, meant that the period of child dependency became even longer and the requirement for very high-energy food – in this case, meat – became even more pressing. Up until now, meat had been obtained in a rather haphazard manner; by scavenging the kills of carnivores or by the (very exciting-sounding) practice of power-scavenging – stealing a fresh kill from the still very present predator. But it was clear that this ad hoc method was no longer sufficient, and more predictable and considerably less dangerous methods of obtaining this vital resource would need to be developed to feed this enormous brain. It is no coincidence that with the emergence of the bigger-brained Homo heidelbergensis we also see the first consistent evidence in the archaeological record for hunting spears. And not any old hunting spears, but 5-foot-long, perfectly crafted wooden javelins such as those recovered from the 450,000-year-old site of Schöningen in Germany. Homo heidelbergensis was not only a skilled hunter but also a highly skilled craftsman.
It was no longer the case that female relatives, all of whom were likely to be nursing their own dependent children, could band together to raise their children alone. The need for reliable sources of meat to feed fast-developing toddlers and provide the mother with adequate nutrition to meet the increasing energetic demands of gestating and breastfeeding her large-brained infants meant that someone else needed to step in to ensure the survival of the species. Someone with the time, energy and skill to hunt for meat and produce efficient hunting and butchery tools. Someone not hindered by the energy-sapping processes of reproduction but still bound by the bonds of genetic relatedness. Someone who could build hearths – an explosion of which occurs in the archaeological record at this time – and control fire, enabling the meat gained by hunting to be cooked, making it easier for small stomachs to digest. Someone who could make it their role, as the children grew and became adolescents, to pass on the skills of tool production and the rules of the hunt. And as hunts became more complex, someone who could teach the vital communication and cooperation skills that were so critical both to the success of the hunt and to the child’s success in the wider social world. And as we know from the introduction to this chapter, that person was dad.
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Unlike our ape cousins, the difference in size between the modern human sexes is relatively small. Men are about 1.1 times bigger than women, while male gorillas are nearly twice as big as females, at 1.75 times as large. This large size is a consequence of the male gorilla’s need to defend his harem of breeding females from other males. In contrast, for the last half a million years we have lived largely as monogamous pairs, where both sexes exercise choice as to who they want to be with; there is no need for men to use physical strength to corral multiple females who have little choice as to who their male partner may be. This closeness in size is critical in the evolution of human fatherhood. In a very neat analysis, evolutionary anthropologist Dr Cathy Key of University College London used this difference in size between the sexes to calculate when human fatherhood emerged. In most species where males are considerably larger than females, the costs of reproduction to a male are significantly higher than those to a female, as he needs to grow and maintain a large body to ensure successful access to mates. However, in humans the costs to a man of reproducing are much, much lower than those of a female; compare the need to grow and maintain a body that is not significantly larger than a woman’s to the costs to her of gestating and breastfeeding a human baby. In these circumstances, Key calculated that it would be worthwhile, in the first instance, for a male to invest some energy and contribute to the care of a female’s children, even if they were not his, to try and increase the chance that he would be looked on favourably as the father of her next baby. However, as evolution favours kin selection – preferentially helping those to whom we are genetically related – so a second stage would rapidly evolve where men would begin to ‘mate guard’ females. This would involve the male spending all of his time in close proximity to the female to ensure that when she next became fertile, a tricky thing to pinpoint in human females, he was there to take full advantage of the opportunity to mate. The downside of this for the male would be that he would remove himself from the mating market and have to move away from a promiscuous, but potentially very productive, mating strategy. This would reduce his lifetime number of offspring and make it even more critical that those he did have survived to maturity to ensure the survival of his genes. As a consequence, he would begin to invest heavily in the children of his mate who, on the upside, he could be sure were his as a consequence of his almost constant presence at her side. Key calculated that the point at which this process occurred in our prehistory – that is, where the costs to the female of reproducing were much higher than those to the male – was, you guessed it, with the emergence of the large-brained but similarly sized Homo heidelbergensis half a million years ago.
And this 500,000-year evolutionary story still has relevance for the fathers of today for three main reasons. Firstly, with the first fathers we see the emergence of the two key characteristics that still define the role of the father today, regardless of where he lives. These are protection and teaching. As this book progresses, I will return again and again to the keen need in all fathers to ensure their children’s survival and to support their learning, particularly in relation to the complex social world in which our species exists. Secondly, it tells us that human fatherhood is not simply a by-product of the male desire to procreate, but that it was positively selected for by natural selection. Evolution is obsessively efficient, and it will only lead a species down the route of a complex change in behaviour or anatomy if it is really the only way to ensure the survival of that species. Human fatherhood could be said to be the epitome of such a change. It was a world-altering change in behaviour with far-reaching consequences for our species, and it would not have been selected for unless it conferred considerable benefits on us. And finally, and perhaps most importantly, this evolutionary story tells us that fathering is innate, not learnt, as we are often led to believe. Yes, you do need to learn all the practical aspects of nappy changing, bathing and feeding, but so does mum. If you have ever seen a new mother struggle as she tries to tackle the skill that is breastfeeding, it is clear that we all need time to learn to be a parent. But your parenting instinct is within you, a lesson I learnt at the very start of my career.
I first studied anthropology under a wonderful primatologist called Simon Bearder. He had made a career studying the tiny, nocturnal bush babies of Africa. In our first lecture, he explained our closeness to our ape and monkey cousins and that, really, we are just a primate with an unusually large brain and an insatiable curiosity, which results in a constant drive to learn and innovate. He explained that in many ways this was a wonderful thing, but sometimes, by constantly trying to be better, we denied our basic instincts and abilities. And
one area in which we did this to our detriment was parenting. As two of the dads in my study found, parenting is a steep learning curve and you may slip up initially, but your instinct to father is strong and will ultimately set you on the right path:
Noah: You’ll get stuff wrong, but as long as you don’t seriously injure them, you just have to . . .
Adrian: Like when she first moved in, maybe four days later we took her out for a really long walk in her Phil and Ted buggy, thinking, Look at our wonderful child . . . [At one point we said,] ‘She’s getting very red, isn’t she?!’ An hour and a half later we’re thinking, Have we put enough sunscreen on? She was a bit pink! And there was the time we were swinging her in the park and, because we didn’t know our own strength, we kind of swung her right round and we were waiting to hear shoulders dislocating! So we didn’t do that again, did we?
Noah and Adrian, dads to Judy (seven)
The message is: listen to your instincts. Tune in to your inner primate, and you will know how to bring up your child. All parents are different, and they will achieve their parenting goals in very different ways. But your anatomy, your brain, your genes, your hormones have all been shaped by evolution to make you a parent. The instinct and ability to parent is there, you just have to listen for it. And dads, that includes you too.