When I was a college student in the 1990s the general consensus was that human evolution basically stopped around 10,000 years ago with the advent of agriculture and that we aren’t going to see any changes in the future. That was a very naive assumption, as it turned out. Not only have many counterexamples been found, e.g. lactose tolerance that came with pastoralism) and immunity towards many infectious diseases that came with domesticated animals in general, but there is also evidence that selective sweeps are still in progress.
My main focus is on human personality and in this regard, Colin G. DeYoung is one of the most interesting researchers in this respect. He has been working on a cybernetic model of personality and a hierarchy of traits, which looks like this:
From a cybernetic point of view, these represent two different functionalities, one seeking maximal stability and one seeking maximal flexibility. It’s surprising that DeYoung does not venture into Evolutionary Psychology as IMHO it is pretty obvious that stability is related to human sedentism and plasticity to nomadism, adapting the environment to the organism’s need vs adapting to changing new environments, respectively.
The Stability traits include all traits that early farmers required for survival: delayed gratification (high impulse control) and detail-orientedness (conscientiousness), higher conflict threshold and a generally cooperative and conformist attitude (agreeableness) Even a less disturbed sleep (higher need for relaxation, sheltered from nature) makes sense in this regard. Plasticity, on the other hand, includes the skills to survive as nomads (quick reactivity/impulsivity, risk-taking, novelty-seeking. Two subsistence strategies are associated with nomadism: foraging and pastoralism, represented by openness (foraging is quite cerebral work which entails encyclopaedic knowledge of flora and fauna as well as elaborate tracking skills) and extraversion. Openness and extraversion are really only weakly correlated, and this is why I think there should be really three metatraits based on subsistence strategies: foragers, pastoralists and farmers.
We can safely assume that in the past 10,000 years there has been a massive evolutionary sweep towards the stability profile. Moreover, I will argue that this sweep is still going on, reducing pastoralist and forager genes in the genome. While our society generally values traits associated with the plasticity profile (creativity, flexibility, curiosity, etc.) modern life is really tailored towards the stability profile. We know that conscientiousness, rather than creativity, is the best predictor of academic and professional success. Farmer types would do best in the vast majority of jobs, some expectations would be firefighters/soldiers (pastoralist types) and scientists/artists (hunter-gatherer types). Musicians frequently have the plasticity profile, often documented by their unstable lifestyle and their songs, such as “Gypsy” (Stevie Nicks, Shakara), “The Wanderer”, “Born to Run”, and “Wherever I Lay My Hat (That's My Home)”.
The plasticity profile is associated with a number of drawbacks for modern life, the biggest one is having limited cognitive resources for prolonged routine tasks. ADHD has therefore a high association with the plasticity profile. Thom Hartman and others have dubbed this profile the “Edison Gene”, which is really not a single gene at all, but a whole complex, but we do know that the dopamine receptor gene is involved. People with a plasticity profile may become highly successful athletes, artists or scientists and inventors, but they also have a higher risk of ending up in prison and a higher risk for mental health problems that have a positive correlation with neuroticism (depression and anxiety) and openness (schizophrenia). “Orchids” is a great descriptor for people with a plasticity profile.
As hunter-gatherer types have the least adaptations for a sedentary farmer life, they are highest at risk, illustrated by the following diagram:
Not having evolutionary adaptations for a “farmer world” increases the risk for these mental health issues. This would also explain the links between ADHD/schizotypy and creativity, ASD and scientific/engineering skills and bipolar and high intelligence. Einstein’s son Eduard suffered from schizophrenia, which makes it likely that Einstein himself had many of the genes that increase the susceptibility to schizophrenia. ASD runs high in families of science and engineering students.
Needless to say that all of these conditions are related to a lower reproductive outcome, which means that selective sweeps towards the stability profile are inevitable. However, this also represents a serious threat to humankind in general, as plasticity and innovation are required for a functioning society. There is a tragic irony here. Proponents of eugenics had it wrong, they wanted to eliminate the very genes that have always helped increase progress in human culture. The Gene Bomb is a 1996 book by David E. Comings that argued exactly that people with ADHD, ASD and learning disorders decrease the average IQ in the general population. If anything the increase in diagnoses is a warning sign that there is something wrong with our society, school system, etc. Unlike Comings believes, neurodiverse people reproduce at lower rates rather than higher rates, which is borne out by the fact that on average they tend to attract a partner and have children (if at all) much later than the general population.
Is there any real evidence that the plasticity profile is waning? Markus Jokela (2012) has found in a study that since the availability of the pill “Higher levels of openness to experience in both sexes were associated with lower fertility [...]”. Geneticist David Reich cites an interesting study from Iceland in Who We Are and How We Got Here (2018) which found that genes associated with higher academic attainment and lifelong learning were fewer in each generation. Academics, who are generally very high in openness tend to have fewer children with women being even more disadvantaged than men. Female professors have higher divorce rates, lower marriage rates, and fewer children than male professors.
I am really looking forward to more research in this area, I think it holds a lot of surprises; I am sure we will want to keep the very genes that make people susceptible to ASD and ADHD in the gene pool rather than wanting to eliminate them. These genes may have brought suffering to the individuals who carried them, but they most likely have also brought about most of the innovations humankind has ever come up with.
For more check out my book
https://www.amazon.com/dp/B09LSF98WV
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