I agree with Gould that human evolution has been driven by the principles of heterochrony, specifically neoteny or changes in the rate or timing of maturation. Stephen J. Gould has been the contemporary advocate for this view. His 1977 Ontogeny and Phylogeny goes into detail. It’s one of those dozen books that I’ve read several times (along with books by Tolkien, Hesse, Castaneda, Bandler & Grinder, two Buddhist texts, and Gary Larson’s The Far Side).

Gould could have gone further, exploring the physical manifestations of neoteny in the human evolution fossil record. This quest perhaps reveals more riddles than answers, but I suggest that it’s a fruitful exploration nonetheless.

I hypothesize that the engine behind neoteny is social structure as testosterone levels rise and fall with an emphasis on either matrifocal or patrifocal societal orientations. Mother testosterone (T) levels are high in a matrifocal society. Here the females are commanding, autonomous and central to hunting/gathering societies. Mother testosterone levels are low in patrifocal society. Here the females cooperate with commanding, hierarchical, highly competitive males, and the females adjust to a male-centric point of view. It is the mother’s testosterone level that determines her children’s testosterone levels and maturation rates at the sixth week before birth. By determining maturation rate, the mother’s testosterone level reinforces or decides social structure. High T women mate with low T men in matrifocal society. High T men mate with low T females in a patrifocal society.

There is a feedback loop. Mother’s testosterone level > maturation speed > social structure > mother’s testosterone level. The environment can intervene at all three levels of the loop by influencing maturation rates and timing, thus modifying the trajectory of human evolution.

The trajectory is not a line, but a series of waves. We did not evolve seamlessly from a chimpanzee-like progenitor to the humans of today, becoming more and more neotenous directly. We meandered forward along a snake-like evolutionary path as social structures veered, sometimes in a more matrifocal direction, sometimes in a more patrifocal direction.

We can trace this meandering path as it reveals itself in the skeletons of our ancestors.

Gracile equals matrifocal, neotenous cultures. Robust suggests more patrifocal, non-neotenous societies. This classification is somewhat complicated by the fact that “gracile” and “robust” refer to both sexes. In a matrifocal society, it is the man that is more gracile and the woman more robust, and in the patrifocal society, it is the male that is more robust and the female gracile. Because it is the male that seems to more physiologically manifest the repercussion of social structure, the terms “robust” and “gracile” seem to stick to the male.

The reason that the male may modify more than the female is that in societies that demand greater male strength, either because of competition among males or environmental threats, there is greater sexual dimorphism or larger size and weight difference between the male and the female. Societies that are threatened or that compel males to physically compete propel society in a patrifocal direction. During these periods of our evolution, we would not necessarily evolve quickly in a neotenous direction. But it is assumed that it is when the male is heavily selected to exhibit neotenous features that humans most quickly evolve in that direction. Why wouldn’t humans evolve toward neoteny when females exhibit neoteny in a patrifocal social structure? I believe it is because sexual selection drives evolution fastest when females do the selecting. Females are far more discriminating. This discrimination probably has something to do with estrogen. Those compelled to pick very specific kinds of mates are those that decide the direction that evolution takes.

Complicating the gracile/robust frame is the physiological sexual dimorphism that is present in a matrifocal society. Neoteny tends to elongate the limbs and arms of males and females, particularly when the timing of maturation brings pubertal onset later in ontogeny. In a matrifocal society, where there would be less sexual dimorphism because of less intramale competition, males will tend to be lanky, women not, thus exaggerating the height differential between the sexes.

I’ve not read any studies that explore our evolution noting the principles outlined above. Some academics, such as Swan, Miller and Crow, have touched upon these themes but have never made the connections. Even Gould never explored the repercussions of testosterone on heterochronic theory or made the connection between hormones, sexual selection, patterns in neuropsychology conditions characterized by maturational delay and the fossil record.

It’s difficult for modern males to understand that our evolution has had an enormous amount to do with the decisions of females. It doesn’t help that Engels and Marx suggested this position. For an academic to have explored as many disciplines as this theory of human evolution relies upon, that academic would likely have to resign himself or herself to not being able to achieve status in his or her chosen discipline because he or she would be unable to compete with peers concentrating in a single area. Publishing would be a challenge.

The great Gregory Bateson, husband to the commanding Margaret Mead, would be the exception. Steps to an Ecology of Mind is a book I’ve read several times. Bateson, master of several academic departments, saw patterns that leapt from discipline to discipline. Multidisciplinary pattern-sleuth academics are perhaps rarer than those skeletons that point to how we came to be.

Now, with the web, anyone can be an academic. Anybody can careen across an Ivy League campus, leaving deep ruts in green grass, visiting libraries in a jalopy made of a laptop trailing a broadband connection. Making connections is too much fun to leave it to scholars just trying to survive. As competitive as their environment is, you’d think every academic skeleton would be robust.


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This entry was posted on Monday, October 6th, 2008 at 7:10 am and is filed under Biology, Neoteny, Ontogeny, Sexual Selection, Social Structure. 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.
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  1. Los cerebros rosas y azules, no existen. – Los perros de pavolv-a on June 10, 2018 5:03 am

    […] método, empezando a aplicarse los tests de inteligencia. Lo que subyace a estas técnicas, según S. J. Gould, es el planteamiento erróneo de que la inteligencia es propiamente una entidad, una cosa […]

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