Human evolution; our dads are different than ape dads (Introduction)

by David Turell @, Thursday, January 17, 2019, 21:02 (158 days ago) @ David Turell

A new study shows how different:

https://aeon.co/essays/the-devotion-of-the-human-dad-separates-us-from-other-apes?utm_s...

"Among our close animal relatives, only humans have involved and empathic fathers. Why did evolution favour the devoted dad?

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"So necessary is this trait to the survival of our species that it is underpinned by an extensive, interrelated web of biological, psychological and behavioural systems that evolved over the past half a million years. Yet, until 10 years ago, we had neglected to try to understand this trait, due to the misguided assumption that it was of no significance – indeed, that it was dispensable. This trait is human fatherhood,

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"To understand the role of the father, we must first understand why it evolved in our species of ape and no other. The answer inevitably lies in our unique anatomy and life history. As any parent knows, human babies are startlingly dependent when they are born. This is due to the combination of a narrowed birth canal – the consequence of our bipedality – and our unusually large brains, which are six times larger than they should be for a mammal of our body size.

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"This has meant that, to ensure the survival of mother and baby and the continued existence of our species, we have evolved to exhibit a shortened gestation period, enabling the head to pass safely through the birth canal. The consequence of this is that our babies are born long before their brains are fully developed. But this reduced investment in the womb has not led to an increased, compensatory period of maternal investment after birth. Rather, the minimum period of lactation necessary for a child to survive is likewise drastically reduced; the age at weaning of an infant child can be as young as three or four months. A stark contrast to the five years evident in the chimp. Why is this the case?

"If we, as a species, were to follow the trajectory of the chimpanzee, then our interbirth interval (the time between the birth of one baby and the next) would have been so long; so complex and so energy-hungry is the human brain that it would have led to an inability to replace – let alone increase – our population. So, evolution selected for those members of our species who could wean their babies earlier and return to reproduction, ensuring the survival of their genes and our species. But because the brain had so much development ahead of it, these changes in gestation and lactation lengths led to a whole new life-history stage – childhood – and the evolution of a uniquely human character: the toddler.

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"But 500,000 years ago, our ancestors’ brains made another massive leap in size, and suddenly relying on female help alone was not enough. This new brain was energetically hungrier than ever before. Babies were born more helpless still, and the food – meat – now required to fuel our brains was even more complicated to catch and process than before. Mum needed to look beyond her female kin for someone else. Someone who was as genetically invested in her child as she was. This was, of course, dad.

"Without dad’s input, the threat to the survival of his child, and hence his genetic heritage, was such that, on balance, it made sense to stick around. Dad was incentivised to commit to one female and one family while rejecting those potential matings with other females, where his paternity was less well-assured.

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"Mothers, still focused on the production of the next child, would be restricted in the amount of hands-on life experience they could give their teenagers, so it was dad who became the teacher.

"This still rings true for the fathers whom my colleagues and I research, across the globe, today. In all cultures, regardless of their economic model, fathers teach their children the vital skills to survive in their particular environment.

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"Fathers are so critical to the survival of our children and our species that evolution has not left their suitability for the role to chance. Like mothers, fathers have been shaped by evolution to be biologically, psychologically and behaviourally primed to parent. We can no longer say that mothering is instinctive yet fathering is learned.

"The hormonal and brain changes seen in new mothers are mirrored in fathers. Irreversible reductions in testosterone and changes in oxytocin levels prepare a man to be a sensitive and responsive father, attuned to his child’s needs and primed to bond – and critically, less motivated by the search for a new mate. As a man’s testosterone drops, the reward of chemical dopamine increases; this means that he receives the most wonderful neurochemical reward of all whenever he interacts with his child.

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"Men have evolved to father and to be an equal but crucially different part of the parenting team. By not acknowledging who they are or supporting what they do, we are really missing a trick. Some 80 per cent of men aspire to become fathers. I believe it is time we made the effort to get to know who they really are."

Comment: Very long extremely interesting article. It all seems to be the fault of such a huge brain size and the time to become adult.. No ape does this.


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