Human Alpha Diversity

The human species exhibits a huge diversity of personality types even within small and otherwise homogenous communities. This variation is obvious to all of us. Informal personality profiling of others is a fundamental part of the human condition, and the language that has emerged from that profiling is everywhere, from everyday conversations to our greatest works of literature. More formal approaches to studying personality have been explored from at least the days of Hippocrates, who suggested a two-factor model that categorized people into four groups: Phlegmatic, Choleric, Sanguine, and Melancholic, a theory later expanded by Galen. Modern psychologists generally recognize the 'big five' axes of personality variation of openness, conscientiousness, extraversion, agreeableness and neuroticism, although there are alternative approaches to personality profiling, for example the Myers-Briggs test that is often used to help understand group dynamics in a business setting. Importantly, all local populations that have ever been tested have shown marked variation along all of these personality axes. You find sanguines in the plains of Africa, open extroverts in the mountains of Tibet, ENTJ's in Vanuatu.

How can this diversity persist? Why, during our evolution, didn't the humans with the best, most optimal personality type outcompete all the others, leaving behind only those genes that encode the optimal personality?

Ecologists use the term alpha diversity to refer to this kind of local, small scale variation in measurable traits. Ecological theory provides two explanations for alpha diversity – difference advantage and group selection. What these explanations share is a view that diversity is functionally advantageous. The implication is that personality diversity is not an evolutionary accident, but something that has evolved over millions of years because it improved the prospects of individuals, and / or the groups to which those people belonged. This view of personality diversity, as something that was, is, and will be necessary to our individual and collective wellbeing, has radical implications for every part of our society, especially the ways in which we educate our children (see below).

As I outline in a separate essay, difference advantage occurs when, all else being equal, there is an advantage to being different to the others in your community. For difference advantage to explain personality diversity, we need to hypothesize that, in a population that becomes dominated by one or a few personality types, the rarer personality types are at an advantage. For example, in a population of closed introverts, open extroverts might be at an advantage because they are more interested in exploring new opportunities. But we need the converse to be true also – in a population of open extroverts, closed introverts need to be at an advantage. Whilst theoretically possible, I find it hard to imagine this mechanism operating in any but the most general terms. I cannot think of a single concrete example.

In contrast, the other mechanism – group selection – seems like an entirely plausible explanation for human personality diversity. Group selection occurs where traits survive because they confer an advantage to the group. If the group advantage is large enough, it can select for traits that are actually disadvantageous to some individuals. Group selection can also select for a mixture of traits, rather than just one type. And importantly, group selection does not need to select for group harmony! In the same way that our bodies are full of antagonistic muscles that lead to optimal control of limbs, so group selection can, in principle, select for conflict and competition among group members, if this is sufficiently beneficial to the group. Perhaps then, introverts are always at a disadvantage to extroverts, but introverts are retained by evolution because they are needed in the mix for the sake of the group. Perhaps populations of all extroverts, or all introverts, have trouble forming the hierarchical power structures that are necessary for rapid group decision making. Groups might need conscientious individuals to keep an eye on the details, but spontaneous individuals to identify new opportunities; and so on. If the group selection idea is correct, we would expect to find a substantial amount of personality variation in all human groups – which is exactly we see. And we might see different personality types clashing and competing, without realizing that this is all good for the group.

Interestingly, much of human evolution occurred within small groups of close relatives, and this is a recipe for a particularly strong form of group selection called kin selection. Kin selection is so powerful because, within a group of close relatives, helping others means helping your own genes. Could the diversity of human personality type have resulted largely from this special form of group selection? That is, could evolution have favoured those family groups that featured a wide variety of personalities? The idea of kin selection for diversity within the family group is rarely discussed, but it makes an interesting prediction. Whereas in general, we expect close relatives to be similar due to their genetic similarity, kin selection for diversity would attempt to make close relatives different to each other. The mechanisms involved are not crucial. All that matters is that, by the time that humans are old enough to play an important functional role in the group, that somehow they had settled on very different personalities. Sure enough, all families that I have known have seemed markedly diverse in personality.

The implications of all this are that every part of our society should recognize that humans evolved first and foremost to be different, in such a way that we work better in diverse groups. Intuitive thinkers and rational thinkers, leaders and followers, paranoids and sanguines, cholerics and melancholics, ENTPs, ISFPs, aspergers, mystics, Ls, Gs, Bs and Ts -- there is no obvious place to stop! The good news is that appreciation of diversity appears to be taking hold in the world of business, as evidence mounts of the beneficial effects of all forms of diversity in productivity (see this other essay). But this will not be enough, so long as the whole concept of diversity and teamwork remains an anathema within our current education systems.

Overall, our education systems value homogeneity and conformity above all else, because they were created to encourage the narrow skill set that was thought to be most important in building and running global empires without information and communication technology. Namely, obedience, neat handwriting, rapid mental arithmetic, uniforms. In order to prop up hierarchical power networks, it was crucial to be able to rank young people so that they could adopt their proper place in that hierarchy (exactly how you ranked them was much less important that the fact they could be ranked at all). Zip forward to today, where, by and large, we teach our children to be quiet, working alone in isolation of the amazing technology that we have built (think, calculators, computers, wikipedia). We force them to use pencils and develop neat writing long before they are allowed to touch a computer keyboard. Rather than encourage personality diversity, we relentlessly espouse the value of exactly one personality type, which just so happens to be the dominant personality type of teachers themselves (who else would want to spend the rest of their lives in the very place where they were forced to repress everything that made them interesting and unique?). If you keep questioning the relevance of this approach to the needs of 21st century society, you'll eventually be told that it's all to do with the need for exams and grades, which in turn are needed to decide who gets to go to university. You could point out that positions in the real economy are, in complete contrast to what children are told, mostly handed out without reference to grades, and ask why university places need to be any different. But you probably won't get very far.

So my hope for 21st century education is that it will, finally, start encouraging, and stop suppressing, the three things that have always defined our species: diversity, teamwork, and technology. Children should come to understand what makes them special, and become expert in playing the roles that they are naturally good at playing, whilst learning to understand and compensate for their natural weaknesses, and learning to work with other personality types. In the meantime, the rest of us can get on with building the future, within a society that looks nothing like our schools.

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