Sexual Selection

I am fascinated by evolution.  I love all of those shows by Richard Attenborough showing the wonderful byways evolution has followed.  I also love all of the smooth explanations about how some bizarre plumage or behavior really helps some animal get more food or hide from a predator or makes them better equipped to breed.

But when it comes to human beings, I begin to have problems.  All of those glib explanations for animal behavior are physical in nature.  That is, when you have some odd physical manifestation, then we look for some physical explanation. When this formula is applied to people, the explanations offered are sometimes pretty silly.

Let me offer the example of our odd (and unique) pattern of maturation.

Human beings, from a gene’s point of view, are just a large, clumsy method of replicating genes.  At least, that is the argument that has been made by some geneticists.  (If they are right, I must be a terrible disappointment to my genes.)  From the purest form of that argument, once we have passed our genes along to another generation, we become superfluous.  And for a lot of species, from insects to salmon, that conclusion is applied with Draconian precision:  You mate, then you die.

Unfortunately for the purity of the we-are-merely-gene-carriers argument, human have an  evolutionary strategy that is just plain contrary.  Most species, if they do not exactly hew to the Draconian model, still try to minimize the parent/offspring dependency phase.  One of the most astonishing parts in those nature films is the sight of a young deer or colt struggling to its feet soon after birth.  Within a day or two, those newborns can keep right up with the herd.  And even for those animals whose young have a real, helpless infancy in their dens, that infancy is a tiny fraction of their life-spans.

Not us.

We do not deliver our young into the world just a step away from independent survivability.
It appears we have selected a very different plan.  (That phrasing is, of course, backwards.  It would be more accurate to say we were chosen than to say we chose.)  Alone in the animal kingdom, we stretch out our infancy over many years.  After that we stretch our childhood over an enormous fraction of our life expectancy.

On the face of it, it is insane to have our young helpless for long years and needing substantial protection for many more years after that.  I think it was Francis Bacon who said, “He that hath wife and children hath given hostages to fortune.”  This method of ours looks like a risibly bad idea, doomed to failure.  In fact, it sounds like one of those sad epitaphs biologists give to explain the fate of some poor, dumb species whose evolutionary choice led to extinction.

Over the years, those folks with the purely physical explanations have offered quite a few trying to justify this strange choice of ours.  One of my favorites is that since as adults we are going to have, proportionately, very large heads, we are forced by the size of the birth canal to complete most of our cerebral development after birth, lengthening our infancy.

Just exactly why the birth canal couldn’t grow any bigger is left unexplained by this theory.  Apparently there is a very tight evolutionary constraint on birth canal size (try explaining that to a mother elephant!) while there are none on how long the young can stay vulnerable.  I find that logic unpersuasive, to put it politely.

I think the problem with all such labored explanations is that they try to find a purely physical explanation for a physical fact.  They try to extend the method that works for insects or birds all the way to animals that have a physical life and a social life and a conscious life.  I think that for  such a creature, all of those elements must form part of the evolutionary equation.  To go back to my example, I don’t think we can understand the ‘why’ of our extended youth without looking at the other side of the equation:  The ‘how.’

Let me back up a bit.  Assuming there will eventually be some wonderful advantage to having such a long period of development for our young, what is it that keeps this period from becoming fatal prior to their reaching maturity?  To put it another way, if the eventual goal is for our species to keep on reproducing itself, how do we keep our slow-growing young alive long enough to reproduce?  (One part of the answer is, of course, the unnatural self-restraint that we exercise to keep from killing them ourselves when they reach adolescence.)

The rest of the answer to that question clearly cannot lie with the (non-existent) defensive capabilities of the children themselves.  For survival of any group is really a multi-dimensional problem.  It is a question of all the defenses, both individual and collective, that might exist.  On that level, our evolutionary choice depends for its success on both the offspring it produces and the social structures set up to protect that offspring while it grows.

Looked at in this light, our social structures should not be considered merely an incidental result of the evolutionary process:  They have become part of the evolutionary process themselves, both driving the evolutionary process and being driven by it.

One of the consequences of this prolonged infancy and childhood is that no one parent can possibly meet all the needs for feeding, rearing, and protecting.  Other species, facing this problem, have made one of two choices:  either the whole troop/clan/kinship group (or some substantial subset) can collectively rear the young or some stable mother/father relationship must do the job.  The collective method is limited to small groups each of whose members are known to each other and participate.  Since human being live in groups substantially larger than kinship groups, collective rearing of the young becomes unworkable.  Hence we have the mother/father partnership as the core of our system of raising children.  Not that our system(s) don’t have collective elements, but parent rearing is overwhelmingly the dominant pattern in human societies.

Note that as this job will last for something like fifteen years after birth of the children, i.e. to about the length of human life expectancy (30+ years) throughout almost all of our history, then the mother/father strategy becomes de facto mate-for-life.

There are many species that mate for life, even within the primates.  However, our system contains some odd biological mutations that must be presumed to be part of the plan.  In every other species that mate for life, the female has a distinct season wherein she is fertile and willing to mate.  Moreover, the female generally produces some strong sign, most often scent, that she is in estrus.

The human animal is different.  Humans can mate at any season and the human female produces few, if any, signs detectable by the male when she is fertile.  (Note:  the human female can and often does present an extensive range of external signals that she is horny.  This is not the same as producing signs that she is fertile.)

It has been rather cynically suggested those sexual oddities are actually designed to help form monogamous pairs.  The theory is this:  The female of many species will take multiple partners, given the opportunity.  Hence the males of such species have to be very careful to maintain exclusive access to the female while she is fertile, thus insuring the survival of his own genes. In the human case, where the male is not sure when fertility begins and ends and the female can mate at any time, the male had better stick around full time if he want his genes to be passed on and not some other male’s.  (This system is not perfect.  As the old saying has it, “It is a wise son that knows his own father.”)

I am sure there are less cynical explanation of how our sexual peculiarities help bind our social groups together.  Core idea here is that monogamy is our selected strategy and our modifications probably sustain it.

To summarize the physical and the social:  I think we have to assume there is a utility to our long maturation process.  It produces (say) an animal that can learn from experience, as opposed to being equipped with a complete programming based on instincts, and therefore able to plan for and shape its own future.  In order to achieve this goal,  human beings have evolved a system of social organization that balances the vulnerability of the young with a tight, flexible defensive unit (the couple) embedded in a larger society of human beings.  Neither would exist without the other.  If we want to be a species with our slowly maturing young acquiring experience prior to breeding, then we must be a species with parents involved in life long rearing and protection.

Let me add one more element to our evolutionary mix.  We are physical beings.  We are social beings.  But we are also conscious beings.  Collective benefits are all very well, but we also have to see this option as somehow a good idea as well.  Both for society and for us, as individuals. The final question we might ask is how our thoughts and feelings help support the evolutionary path we have chosen.

Over the millennia, our species has tried many modes of establishing those mate-for-life relationships.  We have had arranged marriages that were more about property than anything else.  We have had marriages that were more about the unions of families than about individuals.  We have had marriages that were far more about duty than affection.  And, of course, we have had marriages based simply upon the love between two people.

It could certainly be argued that the pure love version has been the least successful method of creating mate-for-life couples.  Nevertheless, it makes use of powerful forces within the human psyche and tries to yoke them to serve the species’ good.  Above all, it taps into love as a prime motivator in bringing people together.  As a human motivator, it ranks right up there with lust.  And it is at least arguable that it lasts longer.

Understand, I don’t claim to understand all of the ways love’s quixotic rules serve the goal of our evolution.  I just see it as a one of the components of our own unique brand of monogamy.  And I would argue that it is monogamy that has built the social matrix that has allowed us to have those slow-growing children who have presumably been more intelligent and more foresighted than their competition.

So when we seek, however desperately, for some love of our life, let us remember we are not just being selfish.  We are doing our little bit towards working out our own evolution.

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