Evolutionary Biology of Hormonal Responses to Social Challenges in the Human Child by Mark V. Flinn
“‘The mass of men lead lives of quiet desperation.’
-Henry David Thoreau (1817-1862)
And why was quiet desperation such a widespread malady back then, and especially among men? Yet again I trot onstage the only real villain in my story: the oversize human brain.”
– Kurt Vonnegut, Jr. Galápagos
As anyone who has had a family, a relationship, or any human interaction whatsoever can tell you, other people are psychologically taxing things to deal with. So taxing, in fact, that early exposure to stressful events has lifelong (deleterious) effects. Our social environments and our health are inescapably linked, most likely thanks to the neuroendocrine system. So why, given the high and seemingly maladaptive costs that psychosocial stress puts on humans, would natural selection have favored links between psychological mechanisms, stress, and overall health?
The article’s author has this answer: “Hormonal stress response to psychosocial challenges facilitates the neural remodeling and potentiation that is necessary to adapt to the dynamic informational arms race of the human sociocultural environment.” Basically, our social environments are so complex and ever changing that we need ways to restructure them to adapt. To paraphrase the author, the links between psychosocial stimulus, emotion, and stress response may guide the neurological plasticity needed to adapt to the dynamic aspects of human sociality.
Normally, in mammal groups that live with multiple males, there is no paternal (not parental, like I kept reading originally) care. This is because none of the dudes can be QUITE sure that that particular kid is theirs, so why bother? It’s probably Billy’s kid anyway, right? Well, because of our tendency to have exclusive mating relationships (AND the fact that other males tend to respect this relationship) there are reliable cues for the fathers to determine which children are their genetic offspring, and are therefore more likely to care for them.
The human brain evolved rapidly and has high metabolic costs, so the advantages must outweigh these costs. Because of our complex societies, humans must be able to mentally represent the feelings and thoughts of others and have exceptional linguistic abilities for transferring information from one brain to another, enabling complex social learning.
As already stated, our mating habits are different, therefore our kinship systems are different. Our kinship is a key organizational principle, and link families into broader cooperative systems that provide additional opportunities for alloparental (parenting in which people other than the biological parents take part) care. Few species live with overlapping generations that have significant social relationships (i.e., grandparents!). The author argues that the emotional and cognitive processes that guide these relationships must have evolved because they enhanced survival and reproduction of future generations. Aside from these physical basics, grandparents can provide knowledge or experience that will help the grandchildren in social competition.
Darwin saw importance differences between 1. Selection that occurs as a consequence of interaction with ecological factors (natural selection) and 2. Selection occurring as a consequence of interactions among members of the same species competing with each other (social selection). Social selection can be intense and unending, and may generate selective pressures that cause rapid and dramatic changes. Because of this, social selection is characterized by:
1. Intensity of social selection is high because competition can have strong effects on reproduction
2. Since competition is among the same species, ecological constraints don’t play as big a part. So the traits can evolve in extreme and bizarre directions before they are counter-balanced
3. Because competition is about superiority, the bar is continually raised.
4. Social competitions spurs more social competition – which can lead to flexible social learning responses that be enhance information processing in regard to foresight or scenario-building
These characteristics were generated as a result of runaway social selection. We humans are our biggest selective pressure. The primary mental functions (that are also the most extraordinary and distinctly human) involve the negotiation of social relationships. Culture emerged as a selective pressure on our evolving brains, and our extended childhoods enable us to deal with all the things that come with it.
What about the neuroendocrine system?
Our neuroendocrine systems generate very potent sensations in response to the interactions we have with evolutionarily significant individuals (ex. moms and newborns, brothers and sisters, and sexual partners). Bonding/attachment is central in our lives; it helps in survival and reproduction and provides cooperative relationships. There are obvious pros to having people around you care for and that care for you. But like I said before, the people you care for most also stress you the fuck out.
The neuroendocrine mechanisms that underlie attachment and stress are, as luck would have it for anyone trying to go through life stress-free and happy, intimately related. Two hormones are especially connected to attachment: oxytocin (OT) and arginine-vasopressin (AVP). For example, in breast-feeding women, the babies suckling raises OT levels which, among other things, results in a calmness that is conducive to remaining in contact with the infant AND shifts energy from being externally directed to internally in the realm of nutrient storage and growth. Cortisol also has big effects on the body. Mothers with higher cortisol levels are more affectionate, more attracted to their infant’s odor, and are better at recognizing their baby’s cry.
Attachment has some interesting side effects. One which I thought was particularly interesting is that among humans, the neural regions associated with social judgement and assessment of the intentions and emotions of others are somewhat deactivated during the attachment phase. This includes not only bonds with offspring, but also falling in love with a mate. This suggests possibly links between psychological mechanisms for attachment and social relationships. So if you’ve ever run into an ex and thought, “What the hell was I thinking!?” well, you probably weren’t. Your brain shut off temporarily.
“What made marriage so difficult back then was yet again that instigator of so many other sorts of heartbreak: the oversize brain.”
― Kurt Vonnegut, Galápagos
But aside from horrible relationship mistakes, the human mind evolving to respond this way can have other effects. Because of the bonding formed in childhood, the family and kin networks are able to provide cognitive landmarks for the development of a child’s understanding of their social environment. This is good if the family and kin are present, but if they are not, it can be highly deleterious to a child’s health. Psychosocial stress is associated with an increased risk of infectious disease and other illnesses, and chronic/traumatic stress can diminish overall health, because resources are diverted away from important health functions.
Remember cortisol from about two paragraphs ago? Not only important in mother/infant relations. It is a key hormone that is produced in response to physical and psychosocial stress. It regulates many things, such as: energy release, immune activity, mental activity, growth, and reproductive functions. So it’s obviously important. Cortisol release is associated with unpredictable events that require alertness and mental anticipation. It increases your mental capabilities to respond to challenges. It regulates how the body responds to changing environments by preparing it for SPECIFIC, SHORT-TERM demands. But as we all know, stress is not specifically short-term or specific. Chronic stress slows diminishes metabolic energy and makes your autoimmune system tank. That’s why, when everything is seemingly going wrong, you get sick ON TOP OF EVERYTHING ELSE. In kids though, chronic stress means more than just getting sick. It can lead to long term problems. Some develop abnormal cortisol response, which as we have seen, is an important hormone that affects many parts of the body.
Stress and the Family Environment
Children who live with non-relatives or single parents without kin support have higher than average levels of cortisol than their counterparts. Stepchildren have higher cortisol levels than their siblings who are products of both parents in the household. But, it needs to be said this is not true of every child in a “difficult” family environment.
The highest stressing events were most commonly involved trauma from a family conflict or change, and are associated with all ages of children more than any other factor examined. Family interactions are a critical stressor in children’s lives. The most important correlate of the household that affects children’s stress is maternal care. Children in homes without the mother having a mate or kin support were the most at risk for abnormal cortisol and the health problems that go with it.
“Just about every adult human being back then had a brain weighing about three kilogrammes! There was no end to the evil schemes that a thought machine that oversized couldn’t imagine and execute.
So I raise this question, although there is nobody around to answer it: Can it be doubted that three-kilogramme brains were once nearly fatal defects in the evolution of the human race?”
― Kurt Vonnegut, Galápagos
First, apologies for all the Kurt Vonnegut quotes, but I love him and that’s my favorite book of his, so whatever. It seemed appropriate. SECOND – THE QUESTIONS:
The article talks about mothers without mates or kin networks and how deleterious this can be for a child. What if it was the father? Do you think the effect would be the same?
Why do you think some children respond with a high increase of cortisol levels and others do not? Is it biological, or is it perhaps related to a previous life that was unstressful? Is it something else?