It is difficult to imagine that Cro-Magnon males ever worried about their own aggression. After all, the most aggressive males were the ones who fought and bludgeoned their way to the top—to become the alpha males, chiefs, kings, ‘big men’ and rulers of rag-tag Neolithic armies and proto-nation states. By the Mesolithic, hyper-aggression was a ubiquitous male attribute. It reached fixation because it was essential to the transition from multiple populations of post-bottleneck, Upper Palaeolithic humans to a single homogeneous population of fully modern humans.
But by the late Mesolithic, hyper-aggression had become seriously maladaptive. Male coalitions had killed, maimed and displaced so many people that family life and child-rearing were becoming untenable, threatening the viability of the budding species.
This core NP hypothesis is supported by abundant skeletal evidence of mortal injuries, which bioarchaeologist and forensic anthropologist Phillip Walker from the University of California Santa Barbara interprets as strongly indicative of a marked increase in homicide from the Mesolithic onwards.713 Bruce Knauft, a cultural anthropologist who has studied violence in prehistoric times, confirms that by the Mesolithic, the fear of becoming a victim of homicide was a fact of everyday life.714
But if the Mesolithic was dangerous, things were about to get even worse. The frequency of cranial injuries in a sample of Italian bones from massacre sites indicates the level of violence actually rises sharply during the Neolithic.715 Walker points out that this escalation challenges the commonly held view that Neolithic agriculturalists were more peaceful.716
Neolithic men were not only extraordinarily violent, but the butchered human bones excavated from Neolithic sites like La Baume Fontbrégoua in south-eastern France tell us they sometimes also ate their victims.717,718
Male hyper-aggression was now out of control and threatened the viability of the entire human race.
But here’s the catch. The more lives that male hyper-aggression claimed, the more selection pressure was generated for adaptations to curb it. NP theory identifies seven adaptations which appear to have emerged almost exclusively to rein in deleterious male aggression. While undoubtedly helping to curb the death toll, they also added seven new pieces to the complex web of human nature and human physiology. In this respect, they provided a ‘last minute’ fine-tuning of the species. They are some of the best things to come out of Neanderthal predation. It was these last seven modifications that transformed Cro-Magnons into humans beings.
The first adaptation against male hyper-aggression, not surprisingly, was natural selection. Archaeologists digging at 11 eastern Mediterranean sites ranging from the Neolithic to modern times reported that the number of head and neck injuries in males increased dramatically during the Neolithic, reflecting a marked intensification of intergroup male violence.719 Several field studies from the European Iron Age confirm that trauma injuries of all kinds are strikingly more common in males than females.720
These data show that not only were things getting more violent as humans entered the Neolithic Period, but that the violence was being perpetrated mainly by men against other men.
Applying simple Darwinian theory to this situation predicts that over time, the marauding gangs of testosterone-charged homicidal killers became too violent for their own good.
Gradually, the constant intergroup warfare killed off many of the most aggressive young males—the very ones at the forefront of the fighting. And with them went some of the most virulent genes and teems predisposing hyper-aggression in post-pubertal males.
Archaeological data does not reveal what proportion of hyper-aggressive males were culled by natural selection, but research into warfare among modern hunter-gatherer societies provides some clues. In 1970, American anthropologist Karl Heider spent two years in the remote central highlands of West New Guinea studying the Dugum Dani, an isolated group of very aggressive hunter-gatherers. Heider reported that almost 30 percent of Dugum Dani men were killed in warfare.721
A similar story emerges from the highlands of southern Venezuela and northern Brazil, home to a large group of indigenous hunter-gatherers called the Yanomamö. According to anthropologist Napoleon Chagnon’s field study, warfare between some 125 Yanomamö tribes is almost constant, and responsible for the deaths of one third of the total population.722
When anthropologists first studied the Huaorani (or Waorani) group of some 4000 hunter-gathers living at the base of the Andes in Ecuador in the fifties, they reported they were the fiercest, most bellicose ethnic group on earth. Huaorani society was characterised by unremitting intertribal warfare with lethal raiding a ubiquitous feature of their lives. Quarrels over marriage arrangements, accusations of sorcery and blood feuds arising from past killings were common causes of intertribal violence. The researchers estimated that inter-clan skirmishes were responsible for the deaths of a staggering 60 percent of all Huaorani.723
So deleterious was the murder rate that, not surprisingly, over the last 30 years the level of violence has dropped substantially, so that today the Huaorani lead relatively peaceful lives—a testament perhaps to the effectiveness of natural selection.
Given that the Dugum Dani, the Yanomamö and the Huaorani are modern humans and their Mesolithic ancestors were far more violent, we may expect the casualty rate among Mesolithic and Neolithic warriors to be significantly higher—and that those responsible for the killing, raping, razing, burning and pillaging would almost all be men.
These case studies support the contention that by removing or silencing some of the genes and teems regulating male hyper-aggression from the nascent human genome, life for family people in the Neolithic would have gained some much-needed breathing space.
During the period of Neanderthal predation, when human women and children came under concerted attack by Neanderthals because they were soft, sexy targets, women preferred—and selected—aggressive men to protect them. But in the post-Neanderthal era, it is likely that women began to change their attitudes towards aggression, and that this had a direct bearing on mate selection. Those burly, super-macho men with their violent hair-trigger tempers, ready to reach for their spears or axes at the slightest provocation, must have been hell to live with. Ironically, their aggressive behaviour meant that Neolithic men were behaving much like their former brutish adversaries.
This would have altered the women’s choice of mating partners, which nominates sexual selection as the second major adaptation against male hyper-aggression.
For the first time, hyper-aggressive men were passed over by mate- seeking women in favour of more gentle men who, while protective, were also disposed to provide affection and parental support. In this way, sexual selection not only reduced the number of hyper-aggressive men, but also promoted better fathers. In the unimaginably violent Mesolithic and Neolithic periods, choosing a kind man became a proactive adaptive female strategy—providing women with the best chances of surviving long enough to raise their children to adulthood.
Hyper-aggression is derived from the emotional centres of the ‘reptilian brain.’ This means that Cro-Magnon fixed action patterns would have been inflexible, emotional responses. The non-cognitive nature of these behavioural responses is reflected today in psychological attitudes like racism, colourism, xenophobia, ethnocentrism, chauvinism, pack rape mentality, vigilantism, hooliganism and vandalism.
For the most part, these are not specific behaviours. They are emotional states and psychological mindsets that, under certain circumstances, may predispose violent behaviour such as lynching, gang rapes and ethnic cleansing. Once they are triggered, these behaviours are normally resistant to cognitive constraint. A lynch mob in the full frenzy of hatred is rarely responsive to rational argument or persuasion.
Vestiges of this emotional thinking can be seen today in societies besieged by military threats, political upheavals and economic uncertainties—circumstances that discourage rational debate.
Back in the Mesolithic, this suggests that once Cro-Magnons killed the menfolk of a village, there would be no debate about whether to enslave the women and girls. Silent instructions were being parlayed uncensored from primitive neural networks in their Cro-Magnon brains. That’s what made them so dangerous. They were ‘mindless’ and their violence was ‘mindless violence’.
This kind of senseless violence—this kind of man—was ultimately maladaptive, and would have generated selection pressure for new cerebral networks to curb and control Neanderthal fixed action patterns. The massive mammalian brain was already there, it just needed some judicious rewiring—a patch.
So the third mechanism used to counter hyper-aggression was, I suggest, the emergence of cognitive networks able to consciously appraise Neanderthal sign stimuli and, when appropriate, modify or even negate their expression. It was not perfect—but it was a start. Once selected, logic, rationality, objectivity and other higher order cognitive functions would prove adaptive—not only in moderating aggressive fixed action patterns, but in a wide range of other social interactions, such as diplomacy and mediation—and consequently would creep inexorably towards fixation.
Women would quickly recognise the benefits of a smarter man—able to exercise a degree of self-control over his primal instincts and make rational decisions based on information rather than emotional impulses and prejudices. They would increasingly be repulsed by ‘mindless’ men—preferring intelligent fathers for their children.
Indeed, neurobiologist David Neill believes that these kinds of cognitive advances were essential to the emergence of fully modern humans.724 They also fit with the fact that the cognitive and emotional networks in the prefrontal cortex (which controls higher central executive levels of consciousness and rationality)725 are among the most recent neural networks acquired by sapiens.
These networks were important because they not only supported consciousness and self-awareness, but also self-directed autonomous behaviour in the absence of external stimulation.726 Complex forward thinking and behaviour were no longer reliant on sign stimuli. “The result”, Neill writes, “could be that thoughts, acting independent of input from the external environment, could direct behaviour.”727
These upper echelon levels of brain function—possibly for the first time—found fruitful expression vetting, verifying, controlling and negating potentially lethal (maladaptive) fixed action patterns of behaviour.
For example, if a Neolithic mob came across a boy out foraging for fruit, any unusual physical feature, (like the shape of his nose) would normally trigger a fixed action response—with potentially deadly consequences. However, if ‘gut instincts’ could be overridden or even negated by cerebral networks based on logic, self interest, social protocols or long-term objectives, and a rational evaluation ensued, the mob might conclude that, despite the size of the boy’s nose, he was nevertheless one of us and would not be harmed. In the long term, this kind of rational intervention would almost certainly reduce personal violence.
When small hunter-gatherer groups—spreading across Asia, Europe, Af- rica and the Americas—encountered other groups, they would be acutely aware of the minor physical and cultural differences that had accumulated between them. If the differences were considered too great, each group would perceive the other as them—with predictable consequences—until one group eliminated the other.
This dynamic had a direct impact on evolution by removing the most pronounced regional characteristics, and leaving only groups whose acquired regional characteristics were generally (often marginally) accepted by other Cro-Magnon groups as emblematic of us. While they remained acutely aware of differences, they could nevertheless acknowledge their commonality. Those foreigners may decorate their bodies differently, but they do decorate their bodies. And while their clothes were different, they at least wore them.
Sometimes this would be enough to prevent Neanderthal teems being triggered and avoid hostilities between groups. It was also an important step in the gradual homogenisation of humanity, presaging the late emergence of a new and important human adaptation—a degree of tolerance of deviancy.
While the emergence of tolerance may seem paradoxical in the grand scheme of Cro-Magnon evolution and the antithesis of NP theory, it was nonetheless a highly adaptive trait that contributed considerably to their survival rates. As well as reducing intergroup conflicts, tolerance enabled sexual contact with outside groups, which reduced the deleterious impact of inbreeding, such as congenital birth defects, low fertility rates and so on. For nomadic Cro-Magnon tribes, periodically replenishing their gene pool was a necessity rather than a luxury.
Tolerance between isolated regional groups was also adaptive because it allowed people who were slightly different to trade, socialise and exchange ideas and technologies. In addition, it prevented isolated groups from solidifying into a plethora of new species and sub-species.
For Cro-Magnons, swapping genes and intergroup exchange of sexual partners involved families, co-parenting and falling in love, so the capacity to be sexually attracted to someone from an outside group became a kind of litmus test. Because people had to feel enough commonality with each other to form romantic attachments and raise children together, inter- breeding occurred only between groups who were divided by only minor physical, behavioural and cultural differences. And it’s here that tolerance played a major role—in accepting superficial differences in others.
Tolerance provided an evolutionary alternative to speciation. It allowed Cro-Magnons to coalesce into something that may be unique to humanity—hundreds, then thousands of slightly variable regional populations that overlooked their differences to occasionally interbreed. These tribes developed their own cultural identify and while they mostly chose mates from within their group, enough periodically chose partners from outside to replenish their gene stocks. Today, we know these separate but sexually compatible populations as ethnic groups.
Ethnicity describes populations that share similar cultural, religious, physical and linguistic traditions, 728 and who mostly (but not always) mar- ry within the group.729 It is so much part of the cultural landscape we tend to take it for granted, yet ethnicity must have emerged somewhere, at some point in our evolutionary history, to fill an adaptive niche. This new theory of the evolution of ethnicity appears to demonstrate that adaptive functionality. It shows why a primary function of ethnicity is the group’s recognition of its own distinctiveness,730 and as a means of distinguishing us from outsiders.731 This places ethnicity in the ambit of them and us—as yet another mechanism of selection against Neanderthal traits and in favour of human traits.
To function adaptively, ethnicity requires acceptance of deviancy—tolerance—at both a group and individual level, something that would not have come naturally to Late Pleistocene humans. It may have been dependent on the emergence of specialist neuronal networks able to rationally examine sign stimuli and, if necessary, consciously repress fixed action responses.
It follows then that ethnicity was a precarious adaptation—inherent- ly unstable and likely to vaporise into maladaptive responses. Tolerance was the oil that lubricated the machinery of budding ethnicity but, dur- ing the Mesolithic and Neolithic, that attribute would often be in short supply. Famine, droughts, warfare, population densities and other capricious social stresses could affect the interpretation of Neanderthal sign stimuli, so that inconsequential ethnic variations—like clothes, speech patterns and hairstyles—that normally would not trigger Neanderthal teems, now triggered them, sparking violent tribal conflicts which periodically escalated into ‘ethnic cleansing’.
Until now, the adaptations against male hyper-aggression and evolutionary violence have all been biological, and therefore take time. They do not begin to change things until they are close to fixation. For example, it would not be much use if only 20 percent of the women opted for less macho men, or if only 30 percent of men acquired genes that predisposed rational decision-making or tolerance.
This indicates that in the short to medium term, the biological protocols listed would have created a divided society, which included a range of aggressive tendencies. This would gradually coalesce into two camps— one composed mainly of hyper-aggressive young men, aggregated into large ‘proto-armies’, and a second camp, of less aggressive men and women aggregated into families and small tribes for the purposes of raising children. At this stage, both these stone-age groups were nomadic so chance encounters between them would be frequent, and doubtlessly filled with trepidation for the family groups.
During this transitional period, family life and child-rearing would have been possible, but only under extreme duress. Throughout the Mesolithic, and up to the middle Neolithic, the threat of violence to peaceful tribes from pugnacious warrior clans remained destabilising and maladaptive.
If collective violence was as detrimental as suggested by the archaeological evidence, then additional cultural protocols would have been employed to stem the tide of blood. Cultural (non-biological) protocols could impose short-term didactic solutions to bridge the gap—until biological protocols spread to enough of the population to significantly reduce the death toll.