Anatomically Modern Humans first appear in the fossil record around 300 kya, yet we do not leave Africa until 50 kya. So for 250,000 years, we were confined to a single continent.
Perhaps this is an example of what paleontologists Niles Eldredge and Stephen Jay Gould called Punctuated equilibrium, the theory that evolution is not gradual, but rather is a characterized by rapid explosive changes, followed by long periods of stability, followed by rapid explosive change etc.
So from 300 kya to 50 kya may have been a period of stability, since we had acquired the ability to conquer Africa, but apparently couldn’t leave (perhaps because Neanderthals were still superior to us at that point and thus would kill us the second we entered the Middle East, or perhaps we were still too dumb to survive the cold Middle Eastern winters)
Then, as paleontologist Richard Klein has noted, this long equilibrium was punctuated by a great leap forward in adaptive behavior. After spending 250,000 years confined to one continent, our species suddenly colonized five new continents in just 40,000 years.
So our ability to colonize jumped from one continent per 250,000 years to one continent per 8000 years (a 31-fold increase!). What caused this explosive change? Probably some mutation(s) in Africa that gave us the intelligence to leave, (as Klein claimed) quickly followed by natural selection for even more intelligence as we encounter cold climates our tropical bodies weren’t built for (as psychologist Richard Lynn claimed).
In the book The 10,000 year explosion, the authors imply another genetic revolution when agriculture occurred. Indeed
anthropologist John Hawks claims positive selection in the past 5,000 years has been roughly 100 times higher than any other period of human evolution and is quoted as saying ” We are more different genetically from people living 5,000 years ago than they were different from Neanderthals.”
On the one hand, such rapid evolutionary change makes sense. There’s been more technological progress and population size increase in the last 5000 years than in all of previous human evolution combined, suggesting that maybe we’ve become smarter since the neolithic transition.
On the other hand, if people living 5000 years ago were more similar to Neanderthals than they are to us, why are they considered members of our species and not the Neanderthal species? Obviously they’re much more similar to us, at least when it comes to the skeletal traits used to distinguish members of the Homo genus.
Also, brain size has not increased since the end of the Paleolithic and may have even decreased, and our ability to draw (a crude proxy for IQ) , also may have even decreased. CBS news reports:
A new analysis of 1,000 pieces of prehistoric and modern artwork finds that “cavemen,” or people living during the upper Paleolithic period between 10,000 and 50,000 years ago, were more accurate in their depictions of four-legged animals walking than artists are today. While modern artists portray these animals walking incorrectly 57.9 percent of the time, prehistoric cave painters only made mistakes 46.2 percent of the time.
Also, if there’s been such rapid evolutionary change in the last 10,000 years, why hasn’t our ability to colonize new locations increased? We saw a huge increase in colonization ability 50,000 years ago as we jumped from colonizing one continent per 250,000 years to one per 40,000 years, but we haven’t colonized anything in the last 10,000 years, not even Antarctica. This suggests no increase in intelligence since the upper Paleolithic.
On the other hand, we went to the moon which is arguably the equivalent of colonizing a hundred new continents. Or did we? A lot of people think that was a hoax designed to elevate the U.S. above her Soviet cold-war competitors, and while I wouldn’t go that far, if I were a conspiracy nut I would find it suspicious that a) we did this with crude 1960s technology yet can’t seem to do it again today, b) we can go to the moon but we can’t colonize Antarctica, and c) East Asians never went to the moon, despite having the highest IQs.
The strongest evidence that we’ve become smarter in the last 10,000 years is that East Asians score about 14 IQ points higher than Arctic people according to Richard Lynn, even though both are big brained cold adapted Mongoloids that split from a common ancestor before the neolithic transition. Similarly, Lynn found the same pattern in Africa: Bantus score 12 IQ points above Bushmen. This may suggest that the 10,000 year explosion added nearly 1 SD to our IQs. Or it could suggest that Lynn’s data is flawed or that extreme differences in environment (not DNA) explains the IQ advantage East Asians and Bantu have over their hunter-gatherer cousins.