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There’s a theory floating around alt-blogs that human IQ in the developed world has been steadily decreasing since about the dawn of agriculture. The working hypothesis is that agriculture enabled dense urban life to develop, and cities are known population sinks (lack of space/high cost/disease vectors all contribute to lower fertility rates in cities).
The thinking goes that cities attract smarter people, who upon settling into urban mimosavilles promptly forget the Darwinian Prime Directive and fail to reproduce themselves in sufficient numbers. 1.5 sprog per hipster village yenta is a recipe for extinction. (Which is not necessarily a bad thing.)
I don’t know if I buy this theory of decreasing IQ in total, but if true, I can suggest another plausible mechanism that is far more pertinent today, now that disease threat and high child mortality have largely been eliminated. This mechanism is far darker than disease or child mortality, once you get to peering at it closely in your skull ham.
You could call this the CH-ian “The Pill, The Rubber, and Abortion, Oh My!” theory of dysgenia.
The speculative specs: Evolution has slowly, and sometimes quickly, produced human populations with great intelligence (on average). As these population groups gained smarts, they reconfigured their environment so powerfully that their cultures began to exert more influence than the natural world did on how their progeny would evolve.
Gene-culture co-evolution became the order of the day. Civilization sprouted and flourished. And it was good. Until…
These groups of humans became so smart that they outwitted — for a time — the second evolutionary guiding principle of reproduction. They invented Pills and Rubbers and safe and cheap Abortions, thus allowing themselves the joy of sex without the joylessness of changing diapers.
Smarter people, having by their inherent mental dispositions a lower threshold for the tedious and boring tasks of infant care, stopped having so many babies. But smarter people USED to have more babies than dumber people! What happened since then? Well, when pre-20th Century smart people had sex — which they never found boring — they were often stuck with the consequences. Most of them simply accepted the boredom of child-rearing as a necessary component of life.
Once the Era of The Pill, Rubber, and Abortion began in earnest, smart people saw the wisdom, from their own personal hedonistic perspectives, of using these smarthuman-created tools to separate the consequences of boring child-rearing from the titillation of sex. End result: Fewer smarties having kids, more dummies taking up the slack, dysgenia in full black lotus bloom.
For the first time, perhaps, on a large scale, humans had made an end run around a Darwinian First Principle. Humans — some humans, anyway — had become TOO SMART and invented pregnancy-thwarting tech that also thwarted the cosmic, and divine, imperatives. The Pill, The Rubber, and Abortion may be making us dumber!
Hard double-blind, metabolically-controlled ¡SCIENCE! evidence for this “PRA” theory is sparse and mostly circumstantial, but it is out there. For instance, in a study of German parents, having a child lowered their happiness more than any other life change, including death of a spouse!
And of course there are the oft-cited stats of later age of first marriage and lowered fertility plaguing almost the entire Pan Western developed world.
There are countercurrents pushing against the PRA theory of dumbing down humanity. The Pill seems to alter women’s sexual preferences so strongly that they choose less masculine beta males as partners if they were on the Pill during the time of choosing. This would imply that these women would have more kids, Pill-disposed as they are to settling into family life with a beta provider. However, it could conceivably run the other way: Once married and thinking about having kids, women who get off the Pill might suddenly become repulsed by their babyfatted betahubbies as their ovulatory machine revs up again after a hiatus of many years. This could lead to an increase in divorce (which in fact has been happening throughout the West since the 1960s) and consequently a decrease in children (or a decrease in children born in wedlock).
Is the evolution of human intelligence self-limiting? If it is, will societies respond by banning the Pill, the Rubber, and the Abortion? Or will we just have to ride this one out for a few millennia, until the fitness maximizer pendulum swings back to the smart set? Either way, going on the way the West is going now, something’s gonna give.