Consider that human evolution unfolds in a fashion not dissimilar to the way an accordion player produces melody and harmony while inflating and deflating his instrument over time.  The accordion player may observe his audience and modify cadence or change the tune depending on whether folks are dancing, how fast they’re dancing or whether they are paying attention at all.  The instrumentalist’s environment informs the tune he plays and how he plays it.

Human communities are composed of many types of folks.  Not just the individuals in communities are molded by evolutionary processes, but the communities themselves behave like selected targets with those communities that exhibit a variety of useful features that encourage a thriving population surviving and procreating.  This has been called a balanced polymorphism.  A wide variety of human types can contribute to a healthy, balanced polymorphism and a healthy community.

For example, in contemporary society, we observe the artists, caregivers and athletes performing and serving while exhibiting strengths peculiar to their particular neurology, psychology and physical proclivities.  Politicians and business people do what they do best, stoking the economy and growing opportunities.  Aesthetics and usefulness combine to create a satisfying social experience and a balanced society.

It has been hypothesized by neuroscientists such as Norman Geschwind and Marian Annett that there is an arc of human beings in contemporary society that spread from extreme left-handers exhibiting specific useful features to extreme right-handers revealing a different variety of useful characteristics.  Geschwind and Annett suggest that those revealing features of both polarities are perhaps the people best suited to survive and transcend in society, but that the outliers, though negatively impacted by their somatic flirtation with the extremes, and particularly those at the extreme left end of this seamless gradation of individuals, often reveal gifts that the middle zone has less access to.  In other words, a successful, societal-balanced polymorphism encourages a useful, productive status quo often via a sacrifice by those at the extremes.

Annett places an emphasis on language use by hypothesizing that those revealing tendencies toward right-handedness display an enhanced ability to engage in speech.  It seems this occurred at least partly because most right-handed people have experienced a diminution of their right hemisphere by having had synapses pruned during early years.  The left hemisphere, that lobe most inclined to encourage speech, survived childhood unscathed.  Yet, all those at the left end of the spectrum, people often with both hemispheres close to the same size or exactly the same size because the right hemisphere was never downsized, display a variety of skills, strengths and gifts that make their contributions to society a necessary part of the societal balance.  Annett estimates that 30 percent of society fits these left-leaning neurologies, with 18.5 percent being random-handed or exhibiting no tendency toward handedness at all.  The random-handed exhibit left and right-handedness about half of the time.  Almost all of society’s left-handed come from this 18.5 percent.

I hypothesize that two hormones drive the directions that the accordion player uses to guide our evolution with tunes that vary over time.

Testosterone is evident in Annett’s work noting the influence of the random-handed on one side and the strong right-handed at the other.  This was Geschwind’s insight into the process.  Behind Annett’s balanced polymorphism are the low-testosterone males, high-testosterone females on the left with the high-testosterone males, low-testosterone females on the right.  These people are often language-challenged on the left, very language-familiar on the right.  Annett hypothesizes that at the left we have the older genotype, before the appearance of the genes that engaged to compel a diminishing in size of the right lobe, which enhances speech.  The older genotype, the random-handers, exhibit a variety of physical and mental maladies and conditions and do many things extraordinarily well, such as architecture and playing tennis (both have very high percentages of left-handers).  Testosterone controls rates of maturation.  Specifically, a mother’s uterine testosterone levels impact her children’s maturation rates and testosterone levels, a determination made while they are in the womb.  A mother with high testosterone (T) levels births high T females and low t males.  A low t mother creates low t females and high T males.  High T females, low t males are the left end of Annett’s societal-balanced polymorphism.  High T males and low t females stake out the right end of this arc.  Folks in the middle, most of us, exhibit moderations of the left/right themes.

Estrogen is the other hormone encouraging the ways that societies unfold.  Estrogen does not manage maturation rates, but it does two things informing how evolution operates and societies engage.  We live in largely a patrifocal society that has mythologized testosterone for thousands of years.  The impact of estrogen is largely hidden to our eyes, but it is performing the complementary opposite action of testosterone, propelling the balanced polymorphism of society in just that way that the accordion player needs to both expand and contract his instrument to make folks dance.

The evidence of estrogen may not emerge in the handedness appraisals that Annett conducts, with estrogen having no direct effect on maturation.  Still, estrogen compels rates of maturation, even changing those rates by making nuanced determinations.  Estrogen is the foundation of sexual selection.  Estrogen chooses between alternatives, making decisions on which of several is ideal.  Estrogen makes judgments.  The foundation of aesthetics is estrogen.  The peacock tail is a direct result of peahen predilection.  When females pick mates, they choose those males that satisfy a very particular criterion for success.  In addition, estrogen compels caring and caregiving.  Estrogen makes determinations, offers solace, communicates affection.  Estrogen connects.

Testosterone reveals a dynamic whereby the mother’s uterine testosterone levels inform the social structure features of her young.  A high T mom engenders matrifocal progeny, commanding females and cooperative males.  A low t mother contributes to a patrifocal society with dominating males and cooperative females.  There is no evidence, because there have not been any studies, to suggest that a mother’s estrogen levels inform the estrogen levels of her progeny.  Let’s presuppose this to be the case.  Let’s assume that high-estrogen (E) mother’s create high E daughters and low e sons.  Low-estrogen mothers would birth low e daughters and high E sons.  Hypothesizing this to be the case, we would conclude that the outlier or extreme left and right ends would almost always exhibit sexual partners with complementary opposite testosterone and estrogen levels, reflecting family of origin.  At the left end of Annett’s balanced polymorphism you’d have either female Te mating with male tE or female TE mating with male te.  At the right end you’d get male Te mating with female tE, or male TE mating with female te.  Our balanced polymorphism would likely reveal all eight types of individuals, all four pairings.  Still living in a patrifocal society, we’d expect to see something like the 70% drift in the direction of patrifocal prototypes (Male Te mating with female tE, or male TE mating with female te).  Yet, we’d expect to see different societies reveal varying balanced polymorphisms, depending on how social structures are emphasized.

Consider that the accordion melody that we’ve been dancing to has varied over the millennia and around the world.  Consider that Marian Annett’s hypothesized older genotype, the random-handed, is matrifocal-based, evidencing high-testosterone women and low-testosterone men.  Add some harmony by considering that for the last several hundred thousand years, perhaps millions of years, up until the emergence of the gene for right-handedness, we evolved mostly, but not solely, in these matrifocal, random-handed societies with high-testosterone women, low-testosterone men, and estrogen complementing the equation, with the women also high in estrogen, men low in estrogen.

Females were commanding.  Females were exercising choice, choosing males they thought best met their criteria for procreation.  Females chose cooperative, low-testosterone, males.

Other postings on this blog have gone into some detail describing my just-so story hypothesizing the kinds of song-and-dance-driven societies that could lead to the kind of exponential brain-size increases leading to the point that right-handedness became selected.  High-estrogen, aesthetically driven females, commanding females high in testosterone, the females that studies have supported make up the left end of Annett’s balanced polymorphism, are the complementary opposite of the males competing to satisfy the female aesthetic by being the best at what the females want them to do while achieving procreation opportunities, which would be to dance up a storm, delaying maturation, neotenizing, encouraging massive synapse production, slowly over time becoming more human until the gene to diminish the right hemisphere engaged.

I interpret Annett’s work to suggest our origins are matrifocal.  Over the course of our evolution we’d expect to see a matrifocal balanced polymorphism revealing a far larger percentage of the random-handed balanced by a smaller group of low-testosterone females picked by high-testosterone males.  In the event that the environment becomes hostile, the balance could shift, with high-testosterone males moving quickly to become highly valued, particularly if chosen by females for their commanding features.  Ancient societies can shift from matrifocal to patrifocal fairly seamlessly if a wide range of genotypes are always present.  Simply by changing uterine hormone levels, sudden shifts in evolution can occur.

Let me describe an example of how the environment can propel changes in evolution.  An increase of fat in diets in prehistoric societies might have compelled shifts in a different evolutionary, social structure direction.  Patrifocal tribes or bands, moving to a new location or experiencing a change in their environment, might have been introduced to a cornucopia of sustenance in the form of dramatic fat increases.  This increase in fat would have increased a female’s testosterone levels, increased her estrogen levels and decreased the male’s testosterone levels.  The result might have been a sudden shift in social structure, with children produced exhibiting matrifocal features in a single generation.  And, of course, if fat disappears from the diet, things shift back.

Consider the dramatic shifts occurring in our societies today.  Fat increases in diet may be contributing to a surge in a matrifocal direction.  Female choice is becoming the default in the West.  As diets change in Asia with dramatic increases in fat consumption, we may see a fall-off in female infanticide and female foeticide as patrifocal priorities disappear and high T, high E females become common.  (The conventional Asian female is very low in t and e.)  Left-handedness will likely increase as the Asian balanced polymorphism drifts left, allowing increased numbers of the genetically creative and the innovative to emerge in the wombs of women influenced by what they eat.  Formerly stable Asian culture would transform.

The accordion player makes many melodies as he expands and contracts his way across the dance floor.  Watching and listening to his audience to decide which melody next to play, he pays particularly close attention to what’s for dinner.


This entry was posted on Thursday, January 29th, 2009 at 8:38 am and is filed under Estrogen, Neoteny, Ontogeny, Sexual Selection, Social Structure, Society. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
10 Comments so far

  1. Maximilian on June 11, 2009 7:24 pm

    I am a high testosterone male with an artistic/systematic brain. My mother is high testosterone and my father is mid-testosterone, though through his behaviour I’d diagnose low free-testosterone levels.

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