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Why Did Homo Sapiens Become Gentler?

Friday, August 22, 2014 @ 01:08 PM
posted by Rabbi Allen S. Maller
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Although, based on the news media, it is difficult to believe that Homo Sapiens (“HS”) have become biologically gentler, an apparent reduction in testosterone about 50-60,000 years ago led to human personalities becoming gentler and human faces becoming more feminine, according to a new study based on measurements of more than 1,400 ancient and modern skulls. This led people to have gentler personalities and to great advances in art and tool making.

The study, published in the August 2014 issue of the journal Current Anthropology, found that human skulls changed in ways that indicate a lowering of testosterone levels at around the same time that culture was blossoming. The study’s lead author, Robert Cieri, said: The modern human behaviors of technological innovation, making art and rapid cultural exchange probably came at the same time that we developed a more cooperative temperament resulting from having a little less testosterone in action. 

Heavy brows were out, rounder heads were in, and those changes can be traced directly to testosterone levels acting on the skeleton, according to Duke University anthropologist Steven Churchill, who supervised Cieri’s work. What the bones do not reveal, according to a report in The Telegraph 8/3/14, is whether humans had less testosterone in circulation, or fewer receptors for the hormone.

Dr. Hare of Duke University, who also studies differences between our closest living ape relatives, aggressive chimpanzees and mellow bonobos, said chimps and bonobos develop differently, and they respond to “social stress” differently. Chimpanzee males experience a strong rise in testosterone during puberty, but bonobos do not. When stressed, the bonobos don’t produce more testosterone, as chimps do, but they do produce more cortisol, the stress hormone. Thus their social interactions are profoundly different, and their faces are different, too.

Cieri compared the brow ridge, facial shape and interior volume of 13 modern human skulls older than 80,000 years, 41 skulls from 10,000 to 38,000 years ago, and a global sample of 1,367 twentieth century skulls from 30 different ethnic populations. The trend that emerged was toward a reduction in the brow ridge and a shortening of the upper face, traits which generally reflect a reduction in the action of testosterone.

There are a lot of theories about why, after 150,000 years of HS existence, humans suddenly leapt forward in religious activities and technology. Around 40-70,000 years ago, there is widespread evidence of bone and antler tools, heat-treated and flaked flint, projectile weapons, grindstones, fishing and birding equipment, and ritual burials with grave goods.

A significant increase in religious activities in the many millennia prior to that time may have led to increased numbers of people who were able to live together in a band or clan without splitting apart.  Small groups that lack a religious incest taboo will be plagued by the ills of inbreeding. Therefore groups with a religious taboo on incest that leads to exogamy in mating will be selected for.

As ancestor worship strengthens kinship ties over more and more generations, it also expands kinship ties over more nomadic bands creating extensive clans and tribes. These clans and tribes can gather periodically at a special place to exchange future mates. They also started exchanging, i.e., trading for desirable objects not found in their usual local. Seashells, obsidian, red ocher and other materials have been found in campsites and graves more than 100-200 miles away from their closest source.

The stronger the attraction of a special place, the greater the effort that distant clans will make to attend, so gathering spots that are turned into sacred sites of pilgrimage through special seasonal rites will enrich human communities. There are scholars who think that HS advanced trade networks helped them out compete Homo Neanderthals in Europe (studies of Neanderthal DNA have shown that they were a distinct species not ancestral to HS).

The need for all the clans to show up about the same time led to fixed seasonal holy days and a religious calendar. The need to mark time for pilgrimage festivals led people to study the cycle of the moon and the movement of the constellations and thus move some of the spirit powers into the sky. Pilgrimage festivals still have major economic impact and serve in most religions as great sources of religious experience and solidarity.

In small groups moral values can be based on utilitarian principles like “do to others as you want them to do to you,” or “what goes around comes around.” But in larger more complex societies with diverse classes and castes, it may be more effective to root ethics in transcendent terms since there are not enough repeat interactions between individuals to validate utilitarian morality.

As tribes became larger and villages grew, a judge who rewarded good people and punished evil people helped the community to instill its norms in its members. With the exception of a sociopath, the intelligent minds of HS also have a conscious, self-evaluating, purpose driven aspect that needs to be satisfied because groups with a higher percentage of these kinds of minds were more stable and more effective. Guilt arises from many activities and needs to be atoned for. Self-discipline provides many advantages for an individual’s survival and success.

Most people, and all societies, need the structure of rules, community and divine discipline to maintain self-control. Hunters needed to kill animals, yet they obviously felt ambivalent about it because almost all human societies have rules either about offering some of the kill to the spirit of the animal killed, or a taboo on killing or eating certain animals. There are much fewer rules relating to eating plants. Spilling blood intentionally is fraught with spiritual ambivalence and tension that needs to be dealt with.

Sex is also never simply a natural act for HS. The mind is always involved. It is not just chance that the first thing HS becomes self-aware of in the Garden of Eden is the shame of being naked. HS is the only living species that thinks it must clothe itself. Evidence of textiles from more than 24,000 years ago has been found in the cold climates of ice age Europe.

However, the origins of clothing in Africa are the not the result of ice age climate, but the result of concepts of modesty. Self-aware intelligent minds became moral minds, which became modest minds. Recent DNA studies of body lice that must lay their eggs in clothing show that these lice evolved from pubic lice that adapted to clothing that covered the pubic area. This genetic adaptation took place 60-100,000 years ago. Thus, HS have been clothing themselves for at least 60-70,000 years. Long before rules about property became important, religious rules of probity were important.

The authors of the study quoted above argue that living together and cooperating put a premium on agreeableness and lowered aggression and that, in turn, led to changed faces and more cultural exchange. I maintain that religious developments helped make that transition possible and effective by enabling larger and larger bands of humans to live and co-operate together.


Rabbi Allen S. Maller is the Rabbi Emeritus of Temple Akiba in Culver City, California. His website is:  Earlier versions of this article may have appeared elsewhere.

The views expressed by Rabbi Maller are his own and not necessarily those of the Blogmaster. They are published in order to promote this blog’s mission to provide information and foster discussion about matters of faith and science. The Blogmaster thanks Rabbi Maller for his contribution to this forum.

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One Response to “Why Did Homo Sapiens Become Gentler?”

  1. Gnarlodious says:

    You can’t reasonably argue that steadily decreasing testosterone resulted in modern humans because the brutes with more testosterone would have killed them before they had a chance to pass on their defective genes. There is plenty of evidence in archaeology that tells us genocides of more intelligent species occurred consistently through all of evolutionary history. A perfect example is the massacre at Sacred Ridge in southeast Colorado, obviously a genocide against a more modern subspecies despite what anthropologists will tell you. And similar findings of intentional massacres go back into our primitive past. How then, did we humans evolve despite overwhelming forces out to murder any modern mutation? I would propose to you that God keeps a certain gene pool around to extract a new species from, and protects them from the rampaging superstitious primitives out to eradicate them. Its the only explanation that makes sense.

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