A Sustainable Point of View

The Unknown Story of Evolutionary Neurodiversity: A Tale Of Two Temperaments

The Unknown Story of Evolutionary Neurodiversity: A Tale Of Two Temperaments

Neurodiversity is short hand for different biological predispositions for making meaning of the world. In telling this largely unknown story, we can build a meaningful basis for four new paradigms – evolutionary diversity, evolutionary purposeevolutionary politics, and especially important: evolutionary mental health.

This is part two of a story in four parts:

  • We Are All Individuals: The Limits of A Worldview – Individualism is a system of cultural meaning, one that make us neurotic and unhappy and hides an intuitive truth: that we have more in common than we think.
  • The Unknown Story of Evolutionary Neurodiversity: A Tale of Two Temperaments – Though culture often demands ideological conformity, an evolutionary phenomenon called neurodiversity makes that nigh impossible. Neurodiversity is the basis for broad biological differences in how a given population makes meaning of the world; yet, its story – of purpose, politics, community, and mental health – remains largely unknown.
  • A Functioning Cog In Some Great Machinery: Evolutionary Purpose & Mental Health – Neurodiversity evolved as an interaction between culture and genes for temperament; consequently, our cultural environment determines whether we experience that temperament as serving a “purpose,” or as the friction and sparks of mental ill-health.
  • Neurodiversity & Ideology: Politics In The Hive Mind – Just as invisible as our neurodiverse temperaments, are the deep coalitions they form in society, what we call “liberals” and “conservatives.” Politics aren’t battles of reason and logic because each temperament has an incompatible biological paradigm, each with its own unique function in defacto cooperation with the other, even as we busy ourselves with bloody business of the culture wars.

 Temperament, And Why You Should Care

If our differences aren’t really competitive fodder to sort individuals into who is better and worse, what are they really?

In the evolution of a complex adaptive system, cooperation and division of labor are really important. When people contribute different things to the group, they can be working together in ways they don’t fully understand, as their contributions only fit together in a bigger picture they can’t always see. From this vantage point, people cooperate who don’t even know they’re cooperating – artists with accountants, athletes with astronauts, arborists with architects – all working to animate a complex group life that needs each and every one of them.

The skillsets of each of these people are incredibly different from each other. Some require brains, some brawn; some require creativity, some courage; some require dedication, some discipline. Often these skillsets aren’t compatible with one another. What makes for a good accountant might actively work against being a good artist; what makes for a good soldier makes for a lousy priest. That is because our strengths have built in downsides that disqualify people for certain roles, a kind of cost-benefit logic. An artist needs to see things differently from everyone else and be a little unstable. An accountant needs to see things the same way every time and be a little too stable. A soldier needs to follow orders and be a bit of a dick. A priest needs to rise above the fray and see the good in the worst of us. There are two important things here: 1) Our roles are often incompatible; 2) Our weaknesses are often the downsides to unique contributions to something bigger than us.

It turns out this is grist for the mill of an age old question – what is my purpose? The question is more relevant than ever. Through the evolution of human social organization, we have come from tribes of hunters and farmers to idiosyncratic careers in a dynamic society. It has only added to the spice of life that we can tread more unique paths than ever. But it comes with a downside of its own: humans aren’t good with choice; having too many options can paralyze a brain that desperately craves a purposeful goal to guide it.

The good news is that there is one-stop-shopping for questions of differences, strengths and weaknesses, and inborn purpose: evolution. Nature has been evolving complex adaptive systems for thousands of years; it’s got some tried and true strategies for how to add the variety spice to life, and it turns out there is a popular one it keeps coming back to: personality.

For instance, humans aren’t alone in grappling with our purpose in the universe: bees live in complex societies and serve different roles in the hive. But though it would be tempting to think this is a depressing metaphor of a life enslaved to a colorless bureaucracy, that isn’t the case. It turns out that not every bee is equally suited to every role, nor are they pushed into those roles of ill-fit. Hives have evolved bees with different personalities, bees that crave different experiences in the world. Some bees get antsy at the prospect of a day-to-day grind and dream of something more exciting; they dream of flying their own path and contributing in their own way. And the hive has roles for them too.

This is the story of how complex adaptive systems evolved temperament: the biological foundation of our personalities. While cultural individualism would have us believe that we are all blank slates trying to compete to become the dominant individual, the evolution of temperament says otherwise. Temperament suggests that we are not all competing directly, as we’ve evolved to crave different kinds of meaning in order to make different kinds of contributions to our society’s cultural evolution.

Understanding this story can tell us lots about what goals we should look to for a sense of purpose, what it means to have “your people,” where mental health and ill-health come from, and even why politics suck so bad.

Gene-culture coevolutionary theory is a theory of evolutionary selection that operates on groups and their cultures. That is possible thanks to discoveries like Geert Hofstede’s cultural dimensions, showing that idiosyncratic cultures have surprisingly similar dynamics: of individualism/collectivism, masculinity/femininity, power distance index, short-term/long-term orientation, uncertainty avoidance index, and indulgence/restraint.* When you attend to these dynamics, you find that cultural dynamics can be predictable, predictable enough to select for certain genes. When those genes accumulate in the population, they can even shape the cultures reciprocally.

*That these dynamics seem to organize cultures along similar axes to complex adaptive systems may not be a coincidence.

In the case of cultural selection, an important target of selection is temperament genes, which create broad differences in the biological basis of our personalities. I will argue that the evidence shows that those differences work by skewing our biochemical needs for meaning, leading to divergent paradigms, attitudes, needs and drives at a population level. This natural and functional neurodiversity explains our contradictory social landscape while laying a scientific foundation for a couple questions: why are certain kinds of mental health issues associated with certain genes (and why haven’t those genes been selected out), and might the inverse of that poor mental health be something we think of as more spiritual in nature – a sense of social purpose?

Let’s start with how genes interact with something as diverse and idiosyncratic as culture. We’ll use two examples: a temperament gene that lend itself to collectivist cultures, and a temperament gene that lends itself to individualist ones.


Take, for instance, the serotonin transporter gene called SERT (a “serotonin transporter” involved in serotonin reuptake from the synaptic cleft; also known as 5-HTTLPR, 5-HTT, or SLC6A4). This gene has two primary variants around the world, one which codes for a more “efficient” serotonin transporter (a “long” variant), the other less so (a “short” variant). In the US, where 40-45% of the population carries the “pathological” short variant, numerous studies have shown the gene to be highly implicated in mood disorders, a smoking gun for the “diathesis-stress” model of genetically-based mental illness. The evidence is hard to refute – a less efficient serotonin transporter makes for less serotonin in the synaptic cleft, which leads to increased fear and anxiety in the amygdala, where it negatively impacts perceived mood and social status.

However, this finding got flipped on its head when Chiao and Blizinsky at Northwest University looked beyond the gene’s role in individual psychopathology. They found the gene is only associated with mood disorders in the US. In China, where the gene is carried by an astronomical 82% of the population, not only is it not a pathology gene for carriers in the population, the country shows very little problems with mood disorders in general (<1%).*

*Even when controlling for a state history of under-reporting.

The reason for this seems to be a mediating third variable: cultural collectivism.

In the 1980’s Geert Hofstede found that there were several core dimensions in which all cultures differed rather predictably, a hidden order that made their inexplicable dynamics surprisingly sensical. Among the most important proved to be individualism and collectivism. Indeed, it turns out if you plot a country’s Hofstede score for collectivism, you get a relationship between how collectivistic a culture is and how many of SERT short-allele carriers there are. What’s more, the more collectivistic a culture, the more protective this seems to be for the mental health implications of the gene.

Worldwide Distribution 01A

From “Culture–gene coevolution of individualism–collectivism and the serotonin transporter gene” (http://rspb.royalsocietypublishing.org/content/277/1681/529.full#ref-11): Geographical coincidence between serotonin transporter gene diversity and cultural traits of individualism–collectivism across countries. Color maps include all available published data for each variable of interest. Grey areas indicate geographical regions where no published data are available. (a) Color map of frequency distribution of IND-COL from Hofstede (2001). (b) Color map of frequency distribution of S alleles of 5-HTTLPR. (c) Color map of frequency of global prevalence of anxiety. (d) Color map of frequency of global prevalence of mood disorders. Yellow to red color bar indicates low to high prevalence.

One interpretation is as incompatible with our individualistic view on mental health as it is plausible: that the psychological imbalance of low serotonin actually serves a group function.

A genetic propensity for low serotonin makes for an over-active amygdala, which leads to personality traits like loss aversion and harm-avoidanceas well as heightened fear conditioning, increased anxiety and an attentional bias toward negative stimuli.* But counter-intuitively, when you put many such gene-carriers together, it doesn’t produce a society of mental illness; instead, the social order shifts to compensate for the collective defensiveness and sensitivity. A culture arises which values harmony, control, stability, support, security, rule-following and certainty, leading to more rigid hierarchy, ingroup loyalty and a long-term outlook. The result is a culture that insulates the pathological potential of the SERT gene in turn by arriving at what is called an evolutionary stable strategy – an interaction of genes and culture that promotes a successful, or at least stable, form of social organization.

*The common denominator with this temperament is a sensitivity to anticipated negative outcomes. Loss aversion is an attempt to avoid perceived losses due to their disproportionate emotional impact; harm-avoidance is a greater motivation to avoid harm rather than take risks in search of reward; heightened fear conditioning means that fearful stimuli are imprinted easier and provoke a more robust emotional response; greater attentional bias toward negative stimuli means a greater salience to angry faces or poor situational outcomes, for instance.

To Western eyes, this social organization is highly suspect. Not only do we fundamentally suspect any compromises in freedom, Independence and individuality, here we have a system based on “psychopathology”: a population-wide lack of serotonin and greater social sensitivity. But we have to remember that the group-first strategy is enormously robust. China is one of the world’s biggest economies, a global juggernaut that harnesses complex cooperation to pull off tremendous feats of industrial strength. In other words, counter to our Western paradigm, not only do our individualistic judgments ill-prepare us to understand collectivistic culture, our psychological judgments about “pathology genes” may be skewed as well. Perhaps these psychodynamics should not be seen as anything but serving a deep social and evolutionary purpose. Maybe “sensitive genes” are functional genes; maybe the SERT gene isn’t so much a pathology gene as it is a collectivist gene.


A Western analog to the SERT gene is found with the DRD4.7r, a gene that codes for “inefficient” D4 dopamine receptors to create less dopamine in the neural circuits that reward novelty and learning. But taking from the SERT example, this may not be what it seems. In the meaning-making language of this blog, SERT serves its function by increasing a person’s need for serotonin, which increases their drive to get it, leading to collectivism. Similarly, the 7r increases our need for dopamine, and again, our drive to obtain it. The outcome – as seen across a range of studies – is what we might think of as an individualistic gene: a temperament high in traits of novelty-seeking, openness-to-experiencerisk-taking, exploratory-behavior, plasticity, hyperactivity, creativity, and generally being a freak-flag flying weirdo (the degree of which you exhibit these being magnified by whether you have one allele or two).

*other dopamine-regulating genes, such as the DAT-1 and the DRD2, may provide analogs to the 7r for other traits; for instance, the D2’s affect on reward systems make implicate it in extraversion and greater likelihood of alcohol dependence.

As with the SERT gene, Western psychiatry’s individualistic perspective sees the 7r  gene as a smoking gun for the genetic view of mental illness. Everything from ADHDdepression, bipolarhypersexuality, substance and food abuseanti-sociality, low inhibition, and other “pathological” correlations show that this is a bad, bad gene. That is, unless we stop looking for pathology alone. In studies attempting to measure the intersection of genes, coping and social environment, whether the gene was “good” or “bad” had everything to do with the context it was expressed in. In low social support environments, the 7r showed greater receptivity to negative influences and became a sponge for certain pathologies. In supportive social environments, meanwhile, 7r carriers showed something surprising: an advantage. DRD4.7r carriers from good homes showed the most sensitivity to positive interventions, the least negative symptoms, the most prosocial behavior and better attention to high priority stimuli over their DRD4.4r carrying counterparts.* The 7r isn’t a vulnerability gene, it is a sensitivity gene; a plasticity gene; an adaptability gene.

*the DRD4.4r is a variant associated with “normal” dopamine regulation and carried by the majority of gene carriers around the world

From “Cumulative-genetic plasticity, parenting and adolescent self-regulation”; excerpted by “Can Genes Send You High or Low? The Orchid Hypothesis A-Bloom” (http://www.wired.com/2012/03/can-genes-send-you-high-or-low-the-orchid-hypothesis-a-bloom/)

Of course, these contrary findings set up a he-said, she-said of mental health genetics. One side claims that evidence supports the diathesis-stress model of mental health – the idea that there are “vulnerability” genes that are prone to dysfunction if someone has enough bad days – while the other claims the data shows a more complex cost-benefit gene function – genes where a greater sensitivity to the good justifies a greater sensitivity to the bad.

It turns out, though, that there is an elegant way to get at which is more true. The question is this: have these genes been selected for or against in evolutionary history? If it was selected against, for instance, we could infer it has more liability than value; if selected for, the reverse would be true.

The answer seems to be that despite what we would expect of a “pathology gene,” the 7r allele has not been selected against, it has actually been steadily increasing in frequency over time, implying some kind of positive evolutionary value.


We can begin to decode what that positive value might be, because unlike the SERT gene, the 7r has a story.

According to the Max Planck Institute in Germany, the DRD4.7r popped up in the human genome some 37,000 years ago, about the same time humans interbred with Neanderthals in the fertile crescent. Later analysis showed that along with another 4% of our genome, the 7r is indeed from our Neanderthal cousins, unlikely a spontaneous mutation or recombination event. And just after this biological convergence took place, several things happened in quick succession: humans quickly displaced neanderthals in their own niche; humans underwent a cultural explosion in art and tool use, and humans left Africa for possibly the second time to spread out around the world, successfully adapting to every niche in an unprecedented way.

One theory by Garret LoPorto is that the reason we displaced the neanderthals has to do with unique advantages conferred on us by the 7r. While neanderthal groups showed the hallmarks of being exclusively 7r in temperament – they lived in small, musical, warlike bands – humans had a relatively conservative and stable disposition at baseline that allowed for bigger cooperative groups. Only when you put the two together – creativity and complex cooperation – do you unlock what we think of as the unique human character. A new temperamental division of labor saw some people innovating, creating and exploring, while others built a social scaffold under these enterprises, allowing innovations to be retained in culture across generations. This division – what LaPorto called the uprisers and the stabilizers – allowed for a ladder-like ascendance in social complexity. While some group elements were equipped to test new ways of being, new ways of innovating, and new paths and frontiers, others could conserve the learning of previous generations, and maintain a common identity to foster cooperation, by enforcing conformity to cultural tradition.

DRD4.7r 18A

Reconstruction of a Neanderthal child. Red hair comes from the TRMP1 gene, one of the 4% of Neanderthal genes that now makes up human DNA along with the DRD4.7r. Could the legendary fiery temperament associated with red hair come from the 7r? The haplogroup of North-West Europe is associated with a higher frequency of 7r carriers.

Interestingly, this analogy has some cross-species support. Amidst social insects (known for their complex adaptive system dynamics), a similar division of labor exists. In beehives, drones form a majority needed for the day-to-day maintenance work of the colony. The other caste of bees are scouts, tasked with searching out new colonies and food sources, and one way of recruiting for the role is to find bees high in a trait called novelty-seeking. Only with both these groups – the novelty-seekers and their more routine-happy friends – can a colony function successfully. While drones do stereotyped work in lockstep with one another, scouts fly off alone even from one another on a journey into the unknown.* It seems that both strategies – idiosyncratic loners and conformist crowds – have been required of groups going way back in evolutionary history.

*Drawing parallels between social insects and humans seems like a stretch, but the fact is they both follow complex adaptive system logic: human and insect social life are both organized into a kind of superorganism, yielding certain analogous roles and dynamics even as they differ significantly in their “emergent properties”

The analogy goes even further. It turns out, the novelty-seeking trait found in bees is the same trait associated with an individualistic, creative temperament in human beings, the same temperament associated with the DRD4.7r.* And just as in bees, trait-based novelty-seeking leads to a particular outlook in humans: an urge to explore.

*Indeed, even the mechanism underlying the temperament differences – differences in dopamine-signalling – are the same between humans and bees.

The relationship was found by researchers at the University of California, Irvine, where a team found something interesting in the travel patterns of humans after they left Africa. Both with macro-migrations (one-time, large-scale migrations) and micro-migrations (the frequent travels of a nomadic lifestyle), restless travel is highly correlated with the frequency of the long 7r alleles. Namely, groups that historically took longer to travel to their destination showed a greater composition of 7r carriers.

For instance, just 5% of northeast Asians in Eastern Russia carry a 7r allele (for reference, the global average is between 10-20%). However, groups that splintered from that population-of-origin, now called American Indians, crossed the Siberian land bridge to settle in North America after a lengthy migration. These groups show a more-than-modest increase in 7r carriers with an average of 32% carrying at least one 7r allele. Meanwhile, the native populations of modern day Central America, having continued on after their North American peers settled, show still more carriers at 42% of the population. And those who pushed still further south into South America, where they literally ran out of room to roam, sit at a global high 7r carrier percentage with a population average of 69% (some remote tribes like the warlike Yanamamo sit as high as 78%).

This pattern seems to hold throughout the world. From groups that split off from East Asia into Micronesia – where Pacific Islanders (21%) had higher numbers the further they settled from the mainland (5% carriers) – to Jews travelling from Israel – where settlers to distant Rome and Germany had 19%, settlers to the comparatively closer Ethopia had 11%, and those who did the shorter jaunt to Yemen had none. Even within micro-migratory groups, comparing tribes with sedentary lifestyles to micro-migratory nomads, we find on average 10.4% more 7r allele-carriers in the more restless wanderers. Across the world we see that those ethnic populations known to roam are chock-full of 7rs.

Befitting our gene-culture coevolutionary view, authors speculate that the longer a group stayed migratory, the more the resulting band selected for a highly change-adapted, hyperactive personality to populate it. Regardless, it seems that 7r carriers seem to set out just as bees do, pursuing novelty over every new horizon, driven to explore restlessly and finding the threat of danger all the more exciting.

Migration 03B

From “Population Migration and the Variation of Dopamine D4 Receptor (DRD4) Allele Frequencies Around the Globe – a family-based approach”: Scatter plot of proportion of long alleles for the 39 populations by the distance of their macro-migration.

Unlike bees, however, in addition to setting off into the sunset, modern humans may have taken exploration into more abstract domains. By inventing culture and society (among other unique adaptations), humans have opened up cultural evolution, allowing rapid growth in how we cooperate, communicate, plan, reciprocate, innovate, govern, entertain and more. Each of these becomes an evolving way of life in the development of human societies; an evolving social infrastructure that some elements conserve, while others push it toward further development. In this new frontier, exploration becomes a metaphor that spans many different ways of interacting with the world, all linked by the drive that comes from a heightened need for dopamine and the resultant search for all things novel.

That is because in the brain, novelty-seeking is intrinsically rewarding. When evolution made the sense and perception of novel patterns rewarding, it invented curiosity; when it built a brain to imagine and synthesize these patterns, it invented creativity. Novelty-seeking has a relationship with everything from entrepreneurship to spirituality, humor to thrill-seeking, openness to risk-taking, and lots of other traits already mentioned. What is different about DRD4.7r carriers is not how this fundamentally works, only that the existing circuit gets turned up to eleven, creating an insatiable need to explore across realms of knowledge, the psychological interior, cultural meaning-making, technological advancement and so on. These people in turn become championed in social roles like inventor, author, theologian, artist, guru, scientist, comedian, politician, psychologist and other general weirdos, all the human equivalents of hyperactive bee scouts.

Let’s recap. DRD4.7r carriers are temperamental individualists because like bee scouts, they are driven to cross boundaries and break away from social norms in the pursuit of all things new and different. This stacks up over time to create people who see things very differently from a more traditional majority. From a heightened need for one aspect of evolutionary meaning – dopamine and novelty – we get a common temperamental denominator purpose-built for greater flexibility, translating to a thousand diverse lifestyle strategies, all while defying easy categories and paths through life.

While the mechanism for the 7r temperament seems to be an inefficient dopamine receptor, the fact that this temperament has been selected for shows that it isn’t as simple as a genetic vulnerability. The evolutionary justification for individuals who must pathologically sustain the unsustainable – a high need for stimulation – seems to be in order to guarantee a valuable class of people critical to the survival of any evolving group: those uniquely poised to create change, test new things and find new paths forward.

Ironically then, the 7r is a fragmented temperamental community: a common personality platform prone to splinter and diverge from one other as much as from the neurotypical majority. When filtered through a thousand life experiences and other variables (like culture, gender, class and more), the 7r temperament leads to as many idiosyncratic paths: from lifestyle-experimenting hipsters to risk-taking extreme sports enthusiasts; from creative artistic visionaries to narrative-shaping authors; problem-solving engineers to entrepreneurial techies; explorers of physical and metaphorical frontiers to social justice activists; meaning-making theologians; paradigm-pushing thinkers; social narrative-spinning politicians; experimental scientists and on and on. There are different ways to handle this divergence, this bounded culture of the self that can feel like a lonely existential promontory shooting away from the group. Often, 7rs may not even like one another. They may perceive little common ground between them, see common ground as a competitive threat, or fear parallel kinds of eccentricity as forms of crazy (there is a little of that, to be sure). But 7rs can take a different tact, too, seeing themselves as having a foot in each of the 7r communities; a generalist that is part artist, part thinker, part visionary, inventor and change agent. Because the reality is, beneath their superficial differences they share a common evolutionary family bound in common evolutionary purpose: 7rs bestow their cultures the opportunity to evolve new ways to make meaning, interpret worldviews, shape social narratives, and guide knowledge paradigms.

But lest we lose perspective, our temperamental individualists are different from our cultural individualists. Cultural individualists have one natural relationship to each other: competition. Temperamental individualists, however, are defacto cooperators. That cooperation may not be pretty. As uprisers, 7rs may be prone to disdain for the ignorant masses, cynical about the prognosis for change, or seclude themselves from the sad social discourse, yet nevertheless, they find themselves in a reluctant three-legged race with with the stabilizer majority. After all, stabilizers are traditional, dependable, maybe even a little boring and racist, yet they do the thankless work of enforcing a dominant paradigm that happens to conserve thousands of years of accumulated culture and wisdom. The problem, of course, is that that same paradigm is responsible for a status quo full of seething inequities, anachronistic strategies and fantastical barriers to the new information and change, making the uprisers equally important to the ungrateful stabilizers. But let us not forget that uprisers can be frustrating too – full of unnecessary antagonism, pretentious intellectualism, reckless experimentation and heretical truth-telling. Yet when the 7r need to leave the stagnant old ways behind leads them to diverge down a thousand experimental paths, it can sometimes save the stabilizers from themselves.

Thus, while stabilizers value conformity and consensus, certainty and stability, and uprisers value individualism, independence, autonomy and creativity, neither is better or worse – both serve purposes that takes their value from a common mission, despite their mutual antipathy.

Of course, both groups tend to misinterpret their hardwired differences, magnifying the communication barriers between them and weighing down their roles with added friction.

Continued in: A Functioning Cog In Some Great Machinery: Evolutionary Purpose & Mental Health