As best as we can tell from archeological evidence and DNA analysis, for around 96% of human history our choice of mate was largely restricted by geography. Aside from nomadic tribes, nearly all the people who’ve lived and died since we emerged as a distinct species have done so within a five kilometer radius of where they were born.
This means that proximity has played a dominant role in human mate selection and hence in the genes that have been passed down through the ages. There may be “the right one” out there for everyone, but if we’re stuck within the confines of a small hunter-gatherer group or in a rustic hamlet our entire lives the overwhelming probability is that we’ll end up with the nearest least-worst option available.
Since the Industrial Revolution, however, things have changed dramatically. As people congregated in ever-larger cities mate selection options expanded, albeit tightly constrained by class and economics. For all the fairytales about princes marrying paupers, the reality is that nearly everyone married within their socio-economic bracket. Still, even allowing for this, mate selection possibilities increased.
The most dramatic shift has occurred since 1945 in developed nations. As more women entered the workforce and sought higher education, we experienced a radical shift in mate selection choices. For the first time in the history of our species, mate selection became strongly predicated on intelligence (however you care to measure or define the term).
To provide a crude illustration of the phenomenon, Diane and Michael met at work shortly after both of them graduated from university. They are upwardly mobile middle-class professionals, their diet is somewhat more healthy than the norm, and they both play sports. Sharon and Dave didn’t finish secondary education, met in the pub, their job prospects are poor, their diet is atrocious, and they like watching sports on television but are entirely sedentary.
Over the last forty years we’ve seen a clear pattern wherein less intelligent people tend to be overweight and sedentary; in consequence they are far more likely to suffer from hypertension, emphysema, cardiovascular disease, and Type II diabetes. If these trends continue indefinitely into the future, the lifestyle choices made by huge numbers of less intelligent people will lead to selection pressures favoring the development of phenotypical adaptations that to some degree act to counter the deleterious impact of such lifestyle choices.
For example, we can imagine the emergence of physiological adaptations that increase the resilience of pancreatic islet cells, so that a diet high in carbohydrates can be better tolerated. We can likewise imagine the emergence of changes in males that increase reproductive resilience to obesity-induced elevated levels of estrogen. And we can likewise imagine loss of genes associated with high levels of metabolic activity resulting from strenuous exercise, as well as loss of genes associated with elevated cognitive function.
Darwin noticed that the finches living on each of the Galapagos islands were slightly different from each other. He surmised that from a precursor species the descendants on each island had gradually adapted to the specific conditions pertaining. As there was little interbreeding, this process of adaptation eventually led to the emergence of distinct new species. It was this insight that set him on the path to his theory of how life evolves, a theory which has since been confirmed irrefutably thousands of times since then.
We humans have created our own “islands,” not geographically but behaviorally. Thus it’s not difficult to imagine that speciation will likewise occur for us too. Of course, there are plenty of things that may happen to invalidate the hypothesis. If we travel back a mere one hundred and fifty years, or go to many developing nations a mere forty years ago, we’d note that wealth and obesity were strongly correlated because only the wealthy could afford to over-consume calories and lived lives of relative indolence. We’d still make the same predictions regarding adaptations, but the two groups would be reversed.
As we all know, however, the wealthy didn’t continue to swell up; instead they adopted healthier lifestyles.
This occurred partly as a result of education: when we know that something is killing us, we’re likely to avoid it when we’re clever enough to understand that actions have consequences. Low-IQ people, conversely, won’t really grasp the cause-and-effect chain and will simply dismiss inconvenient facts. The change also occurred partly as a result of group internal competition: educated affluent men had to compete for attractive females and females therefore were able to exert selection pressure by means of mate choice. Given two equally affluent males, most females will choose the one in more adequate physical condition. This trend is amplified in the middle-classes where both partners must contribute to the many tasks associated with child-rearing. It’s difficult to be an active and engaged father if you’re waddling around under the impediment of excess weight.
So female selection pressure led to reasonably affluent males making better lifestyle choices, which led to a decrease in obesity rates among the educated population.
Conversely, as the cost of calories (and especially of low-nutrient carbohydrate-based calories) plummeted due to mass production, less intelligent people began to swell up. No real selection pressure is being applied by low-status females because (i) there’s very little foresight involved in their mating practices, and (ii) their range of options is limited due to the fact practically all males in their pool of potential mates will be overweight and thus equivalent rather than differentiated. Without differentiation, no meaningful choice exists and thus no meaningful selection pressure can be exerted.
Yet we must remember that inadequate lifestyle choices have a significant social cost. Today, more than half of all healthcare expenditures in the developed nations go on treating weight-related diseases. Just as the cost of tobacco-related diseases soared during the twentieth century and caused governments to reassess their relaxed attitude toward tobacco companies profiting from selling profoundly unhealthy products, so too are governments eventually going to have to tackle the obesity epidemic, no matter how unpopular such moves will be. Therefore, it is unwise to project current trends in a straight line into the future. We know from history that society, albeit slowly and imperfectly, adapts and adjusts to mitigate harmful behaviors over the longer term. We no longer have slavery, child labor, or treat women as chattels. We no longer permit teachers to inflict corporal punishment on helpless children and we no longer permit men to rape their wives with impunity. Slowly, rules change to address persistent harms.
Does this then mean that speciation will not occur?
Actually, no. Although phenotypes may not diverge as radically as would occur if current trends continued indefinitely into the future, it’s extremely unlikely that we will return to the limited and geographically constrained mate choices of centuries gone by. Even as borders close around the world thanks to mindless populism, intelligent people will continue to mate with other intelligent people and low-IQ people will continue to mate with other low-IQ people. This will undoubtedly result in changes to phenotypes, only more subtle and more concentrated in the genes that code for the many complex inter-connected elements of the brain.
Thus over the course of centuries we can expect to see a divergence between humans who routinely attempt to use their brains for higher-order cognitive functions and humans who go from cradle to grave with the least cognitive effort possible.
The implications for society as a whole are considerable and are unlikely to admit simple solutions.