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Study Claims Human Intelligence Peaked Two To Six Millennia Ago
eldavojohn writes "Professor Gerald "Jerry" Crabtree of Stanford's Crabtree Laboratory published a paper (PDF) that has appeared in two parts in Trends in Genetics. The paper opens with a very controversial suggestion: 'I would be willing to wager that if an average citizen from Athens of 1000 BC were to appear suddenly among us, he or she would be among the brightest and most intellectually alive of our colleagues and companions.' From there, Crabtree speculates we're on the decline of human intelligence and we have been for at least a couple millennia. His argument suggests agriculture and, following from that, cities, have allowed us to break free of some environmental forces on competitive genetic mutations — a la Mike Judge's theory. However, the conclusion of the paper urges humans to keep calm and carry on, as any attempt to fix this genetic trend would almost certainly be futile and disturbing."
...people have been thinking that the past was the "golden era", and that the people of the past were so much better.
Greg Cochran over at West Hunter has a pretty damning critique of this paper.
Cochran's review:
In two recent papers, Gerald Crabtree says two correct things. He says that the brain is complex, depends on the correct functioning of many genes, and is thus particularly vulnerable to genetic load. Although he doesn’t use the phrase “genetic load”, probably because he’s never heard it. He goes on to say that that this is not his area of expertise: truer words were never spoken!
His general argument is that selection for intelligence relaxed with the development of agriculture, and that brain function, easier to mess up than anything else, has probably been deteriorating for thousands of years. We are dumber than out ancestors, who were dumber than theirs, etc.
The first bit, about the relaxation of selection for intelligence in the Neolithic -. Sure. As we all know, just as soon as people domesticated emmer wheat, social workers fanned out, kept people from cheating or killing their neighbors, and made sure that fuckups wouldn’t starve to death. Riiight -it’s all in the Epic of Gilgamesh. In the online supplement.
Why do people project a caricature of modernity back thousands of years before it came into existence? Man, he doesn’t know much about history.
Nor does he know much about biology. If he did, he’d understand that truncation selection is what makes such complex adaptations possible. If only the top 85% (in terms of genetic load) reproduce, the average loser has something like 1 std more load , so each one takes lots of deleterious mutations with him. But then, he’s probably never heard of truncation selection. I’m sure they never taught him that in school, but that’s no excuse – they never taught me, either.
If his thesis was correct, you’d expect hunter-gatherers to be smarter than people from more sophisticated civilizations, which is the crap that Jared Diamond peddles about PNG. But Crabtree says that everyone’s the same – stepping on the dick of his own argument. Of course, in reality, hunter-gatherers score low, often abysmally low, and have terrible trouble trying to fit in to more complex civilizations. They do a perfect imitation of being not-smart, amply documented in the psychometric literature. Of course, he doesn’t know anything about those psychometric results.
Which reminds me of secret clearances: it used to be that having a clearance mean that you were entrusted with information that most people didn’t have. Now, it means that you can’t read Wikileaks, even though everyone else does. In much the same way, you may have the silly impression that having a Ph.D. means knowing more than regular people – but in the human sciences, the most important prerequisite is not knowing certain facts. Some kind soul should post the Index, so newbies won’t get themselves in trouble.
He doesn’t even know things that would almost support his case. Average brain size has indeed decreased over the Neolithic- but in every population, not just in farmers. He might talk about paternal age effects, and how average paternal age varies – but he doesn’t know anything about it. He ought to be thinking about the big population increase associated with agriculture, and the ensuing Fisherian acceleration – but he’s never heard of it.
He even gets the peripheral issues wrong. He talks about language as new, 50,000 years old or so – much more recent than the split between Bushmen/Pygmies and the rest of the human race. Yet they talk. He says that the X chromosome isn’t enriched for cognition and behavioral genes – but it is (by at least a factor of two) , and the reference he quotes confirms it.
Selection pressures and mutation rates can vary in space and time. Intelligence could decrease – it
...The average Athenian lived a life of drudgery and was illiterate...
Those illiterate drudges didn't leave any writings behind.
This guy seems to have studied the people who did write, and the people they wrote about, and came to the astonishing conclusion that the interesting people 2000 years ago were very bright and intellectual. Bah.
All ideas^H^H^H^H^Hprocesses in this post are Patent Pending. (as well as the process of patenting all postings)
What this means, and what conclusions can be drawn... seems speculative to the point of parlour games.
And yet the very facts you adduce lead one almost trivially to the same conclusion as TFA: if anything remotely resembling "intelligence" is both heritable and results in a reproductive advantage, then it is almost certain that we have the least of it of any generation in recent (evolutionary) history.
Nor does one have to go back 6000 years. a few hundred will do, when the human population started its several-ten-fold expansion from a few hundred million to getting on for 10 billion today. That tells us the selective pressure of all kinds have been essentially zero in the past ten-ish generations.
Since we have posited that something vaguely resembling "intelligence" was selected for, and has not been selected for in the past 10+ generations, we can be certain that a lot of dumb people survived to breed who would not have done so previously (me, for example, if we include various kinds of social sagacity in the multi-factor definition of "intelligence").
I've pointed this out in the past on /.: if you grant those two assumptions--even slightly heritable intelligence and an even slight selective advantage for the more intelligent--the complete absence of selection in the past several hundred years necessarily implies we ain't too bright, on average, compared to our historical ancestors.
Blasphemy is a human right. Blasphemophobia kills.
You’re making the assumption that anaclitic ability is the primary determinate of matting success in humans. Normally, it’s not. You can find a few rare cases where it is – and the progeny of those cases tend to have higher rates of autism and aspeger – suggesting that there are tradeoffs.
Normally, a broader range of attributes are used to determine mating potential. The ability to dance is a much better determinate. The ability to process music (mental) in a coordinated fashion (mental / physical) over a long period of time (physical) demonstrates genetic fitness that is hard to fake.
Sigh – and I have 2 left feet.
I don't know, but Archimedes came awfully damned close to inventing it, despite his culture's lack of essential background concepts.
I don't agree with this theory necessarily, but there is a nontrivial theory that explained the Flynn effect in terms of decreased inbreeding. The idea is that inbreeding was more common in the recent past, due to decreased geographic mobility and being tied to specific regions closer to extended families, and that even mild inbreeding decreased intellectual ability on average. With increased mobility and decreased inbreeding, you'd see a fairly rapid increase in intellectual ability. Advocates of this theory sort of tied the magnitude of the Flynn effect to the magnitude of decreases in inbreeding in different locations.
The problem with this model is that as far as I know, the Flynn effect isn't limited to the lower end of the intelligence distribution. I.e., it's not just the lower tail that's being pulled up, it's that the upper tail that's being stretched out at the same time.
I have serious problems with the idea that increased urbanization is somehow isolating us against natural selection. This presumes that natural selection is the primary evolutionary driver of cognitive ability, which may be totally off. There is such thing as social selection (e.g., sexual selection), in which social factors drive the evolution of traits. There's a lot of convincing theory that social selection processes were more important to the evolution of human cognitive ability than natural selection.
Also, as a really basic issue, individuals really low in cognitive ability are not reproducing at higher rates than others--the exact opposite is true. We tend to fixate on certain ranges of cognitive ability, but over the entire range, cognitive ability is positively associated with reproductive success and offspring survival, even in recent times.
I am not so sure about all this. And my uncertainty has nothing to do with political correctness.
First - who guarantees that the least intelligent people on this planet do not carry by accident the most important genes? What if a super-killer disease sweeps above us and a random beggar on the streets of Bangladesh has the genes to fight it? Who says intelligence is the most important quality ? Sure, from where I am standing it seems that it is, but the conditions may change...
Second - why mistake collective intelligence for individual one. Our technological/scientific success (notice that I do no claim success on any other level, like making stable society , improving happiness and human dignity) is a result of the system we build for sharing, accumulating and storage of knowledge. It is not surprising then that the individual scientist , say , is on average less intelligent than Greek philosopher but now we have millions of scientist sharing and checking their findings via the established mechanisms.
Third - this is not news as such. One of the more famous books on the subject by Jared Diamond already claimed that smaller "primitive" societies had to fight different set of challenges which likely make then more intelligent, whereas the civilized folks had to mostly fight with illnesses spreading quickly because we live(d) so cramped together.That is why our diseases were so devastating for them...
Fourth - just an example I stumbled upon last week. A documentary on the BBC showed that what the might of the civilization could not achieve in the 1970 ies indigenous people achieved millennia ago - namely to successfully develop agriculture on one of the most infertile soils on the planet turning it into one of the most fertile and stable soils. You will never guess for which region I am talking about. The Amazonian rainforest. It was amazing revelation - check it out - it's called "Unnatural history - the Amazon". Estimated 5.5 million people living along the river by the time the first Europeans arrived! With cities, roads, education, craftsmanship that rivaled European quality and organized religion. Simple people they were not!
And the most hilarious thing is that every white supremacist I have talked with claims that WE had the more difficult challenges than the "darkies" who just had to sit beneath a tree waiting for the banana to fall, therefore we are genetically more intelligent! I tend to become a tad uncivilized (pun intended) in such discussions.