Human Nature and Evolution

Bruce. L. Gary

The Ancestral Environment

Human nature has many traits that are universal across cultures so there must be a role for our genes in shaping this nature. Some traits can only be explained by viewing them as an evolutionary product that serves tribal genomes, and not necessarily the individuals created by those genomes. For example, tribal interests are served by individuals who exhibit amity toward fellow tribesmen and enmity toward rival tribesmen, referred to as the “amity/enmity complex,” and which is found in all cultures. A tribe is also better able to compete with other tribes if it includes a variety of individual types, such as warriors, artisan craftsmen and leaders, a concept referred to by eusociality theory as having the merits of “division of labor.”

Both examples can be found in other species, such as our close relatives the chimpanzees, so there must be genes for them that have existed for millions of years. Every social species is to some extent “eusocialized” - an adaptation in which individuals behave in ways that serve the collective with no regard for individual welfare. The ants, termites and bees are completely eusocialized, as are a total of 17 species so far identified. Most social species are only partially socialized, and humans are one of these. Patriotism (an extreme version of the amity/enmity complex) and division of labor are central features of human nature.

The number of individual human types is limited because for millions of years our ancestors lived in tribes numbering between 100 and 200. The Dunbar Number of 150 is cited as the largest tribal population that allows for all individuals to know each other well enough to allow for sufficient mutual trust needed for risky tribal tasks. A typical tribe may include 50 adult men (and similar numbers of women and children). The tribe’s welfare will depend mostly on how well the 50 adult men perform while defending the home tribe, or attacking a neighbor tribe, as well as the more mundane activities of hunting, building huts, storing food, etc.

Just as team sports have specialized “positions” each adult male activity in a tribe will benefit from members coming together with special abilities and discovering what they’re good at. Inter-tribal warfare is best conducted by teams with specialized tasks, such as a “lookout” for monitoring enemy status, a commander for coordinating defense or attack, providers of logistical support – and of course front line warriors.

“Group selection” refers to collectives of individuals competing with other collectives. For humans the collectives are tribes. Whereas it is common to speak of tribes competing with each other, it can be more useful to view the competition as between “tribal genomes.” After all, every individual is assembled by genes that are just one subset of the genes residing in the tribal genome, so a tribe is merely one typical example of what the tribal genome is capable of creating.

During the immensity of the human evolutionary past, lasting several million years for some traits and up to 1/3 million years for others, individuals have been created from a tribal genome with different talents. More warrior types are needed than the artisans who create the weapons used by the warriors. A small pool of leader types is needed for recruiting one leader at a time. A diversity of talent should in theory produce numbers with each talent that reflects the need; this is a well-known feature of sociobiology known as “evolutionarily stable strategy.”  Thus, if an optimum ratio of warriors to artisans is 10 to one, then on average a tribe will have 10 times as many warrior types than artisan types.

An effective warrior will have a different personality than the artisan. The warrior will be pugnacious, prone to violence, and he will hate and want to kill strangers. After all, everyone in the home tribe is known, so the only strangers he could encounter would be members of another tribe. An effective artisan would be handicapped if he had the warrior’s personality. He needs patience and carefulness for his chipping, or whittling, to produce the best weapon. A tribal chief will likewise need different personality traits from the warrior and the artisan. The skills he needs are mostly people-oriented.

On theoretical grounds, therefore, we should expect to find different personality traits within every tribe, or among any population. In a well-functioning tribe we should expect to find that each personality type is “well adapted,” i.e., functioning in their assigned task with an accepting attitude.

The Holocene Challenge

About 10,000 years ago the Earth’s climate warmed, as happens at approximately 100,000-year intervals. We are still in that warm epoch, called the Holocene. The improved flora and fauna allowed tribal territory to shrink (actually forced that shrinkage since there are penalties for defending a territory larger than needed for a tribe’s population). This brought tribes closer together, and ancient rivalries led to more frequent inter-tribal conflicts. There had to be a first occasion when two tribes coalesced and became victorious over all rivals. We know this is true because super-tribes dominate the Holocene.

But there were new risks for super-tribes, reminiscent of those that kept all tribes prior to the Holocene close to the Dunbar Number. The simplest risk to understand is that in the new social setting most members of the super-tribe were strangers. The warrior type was constantly discontent with continual encounters with strangers. The super-tribe chief had to impose restraints on the instinctive desire by the warrior to confront strangers. The artisan didn't care; for his type had never had a problem with strangers.

A super-tribe can have a different “evolutionarily stable strategy” profile than for a small tribe. First, there can be more personality type niches because the super-tribe is so large. But this new opening for new niches has a downside, for it creates parasitic niches. Consider the psychopath. In a small tribe, where everyone knows everyone from a wealth of past interactions, the psychopath with his lying, cheating, unpatriotic and self-serving behaviors can’t exist; his true character would be discovered and he would be avoided, or possibly even banished from the tribe. But in a super-tribe the psychopath can do his cheating deeds and relocate to another part of the super-tribe that has no awareness of who he is. On theoretical grounds we should expect to see the incidence of psychopaths increase during the Holocene. It is currently 0.8 % among men, and 0.1 % among women, and there is some evidence, and much speculation, that these numbers are increasing.

The super-tribe can support large cities, surrounded by farms. The personalities that prosper in a city differ from those needed on their rural surroundings. On a farm self-reliance is important, whereas in a city every little problem has specialists waiting to be called on for help. Rural and urban cultures have evolved apart during the Holocene, and by now they are as miscible as oil and water; our politics attests to that.

Personality Mismatches

Evolution has its way of measuring people. It works mostly at the tribal level – a tribe that functions well dominates tribes that don't. This means that a tribe that “victimizes” its individual members for enhancing tribal performance can prosper. The most extreme example of this is the warrior. He inherits a personality that is attracted to a “no questions asked” version of patriotism. When a tribe is preparing for inter-tribal conflict, either picking on a smaller tribe or preparing for an attack by a larger tribe, it is important that everyone in the tribe be motivated to contribute to tribal victory in whatever capacity they can. Therefore, evolution has created a personality trait that enforces widespread patriotism at these times. I argue that this trait can reside in many people and only be expressed when needed.

The test for Right-Wing Authoritarianism, devised by Altemeyer (1981), measures this personality trait. It seems to vary with conditions, so it varies in a given society on timescales of a few years. It is a "latent" personality trait that is present in some fraction of people (e.g., 40 %). It is expressed in a population with a range of incidences at any one time (currently, 6 to 26 % among North America and Europe). I refer to people who have this trait, expressed or not, as “Enforcers.” When the Enforcers are triggered to express this trait they can be annoying busybodies claiming to promote patriotism upon everyone else (whether patriotism is actually appropriate or not).

How should we view the Enforcer? This trait can change from latent to manifest by a trigger condition. In the small tribe the trigger was simple to detect: “Is inter-tribal conflict brewing?” But in a super-tribe the trigger can be a person who is an opportunistic, rabble-rousing psychopath. Such a person can bring about this transformation when there is no need for it by the duped society (however, the needs of the psychopath are met).

In the tribal genome, in the ancestral environment had a voice it would say that the warrior and the Enforcer were good and valuable. Their measurement was tribal genome survival, with no regard for individual welfare, or especially individual understanding of a larger reality. For Evolution, warrior = good, Enforcer = good, skeptical questioner = bad.

The warrior and the Enforcer cause immense suffering in this Holocene world. If only one tribe has warriors, all tribes must have warriors. And every tribe that needs warriors, also needs Enforcers. If Evolution created a personality test it would “norm” the test in a way that bestows sanity upon the warrior and Enforcer, and it would declare the peaceful and cynical skeptic insane!

Only humans create personality tests, so what do these tests conclude? One internet source (link) states that “… approximately 20 % of Americans … suffer from a diagnostic mental disorder in a given year” and “5 % of adults are affected so seriously by mental illness that it interferes with their ability to function in society.”

How ironic, considering that evolution has been refining human nature for millions of years.

The answer, of course, is that humans are living in a social setting for which we are not adapted! Super-tribes have created for the first time this mysterious thing called “civilization.” As Freud wrote, humans are discontent with civilization. A super-tribe civilization was created by accident, by humans (the artisans), and only some of us are pre-adapted to it. The warrior and the Enforcer, the natural leader and most of the small-tribe heroes, all of them are mal-adapted to civilization.

People who cannot function well in a civilized society can’t be blamed for their predicament; it is simply their bad luck to have been born at the wrong time - into a civilization. No wonder so many people speak emotionally about going back to a lost paradise. They would be more comfortable living in a small-tribe, uncivilized. It is fair to state that almost everyone born today is a time-traveler forced into an alien setting for which they are not adapted.

Those who have read this far are among the few who belong here, who are comfortable in a civilization that our like-minded forebears created.

Additional Reading

An extensive treatment of these ideas is in a book available at It has five ratings, and all are 5-star. Here’s the link for it:




This site opened:  2022.12.12.  Last Update:  2022.12.12