Cro-magnons were the first truly human Europeans and have long been romanticized as the first truly modern humans, in part because of a Euro-centric bias, but also because they’re the people most associated with the Upper Paleolithic revolution and the replacement of the Neanderthals who had held our ancestors captive in Africa for hundreds of thousands of years.

They had wonderful lives, wandering through the forests of Europe as the seasons changed from summer to snowy winters, sleeping under the stars, exploring a vast uncharted terrain with a child-like awe of the unknown and rich mythology to explain it, vastly out-competing their only rivals the Neanderthals for food and shelter, and hunting so much mega fauna that they reached their full genetic potential for height and brain size, unlike the stunted malnourished people who would follow them once agriculture was invented. These were some of the happiest people to have ever lived and they did so in a true Garden of Eden, before tempted by the metaphoric apple into the “sin” that was agriculture. A “sin” we would pay dearly for.

But how intelligent were they? This is a tricky question because based on brain size, they appear a bit more intelligent than Europeans today, but based on polygenic education scores, they appear substantially less intelligent.

Brain size suggests Cro-Magnons had an IQ of 104

Over the 20th century, brain size, IQ and height in the developed World has increased thanks to advances in nutrition and reduction in disease allowing us to recover the genetic potential not realized since the Upper Paleolithic, before agriculture had stunted us (Lynn, 1990). Despite brain size in 21st century America reaching an impressive 1418 cm3, (Pumpkin Person, 2018) it’s still less than it was 40,000 years ago, when brain size peaked (mostly in Europe) at about 1487 cm3 (after correcting for preservation bias). So it seems the remaining 69 cm3, shortfall (0.76 SD) is a genetic loss.

But why did genetic potential for brain size decrease 0.76 SD? Perhaps in part because genetic height in Europe decreased 0.5 SD (Piffer & Kirkegaard, 2024) and polygenic height scores correlate 0.64 with height, and height correlates 0.4 with cranial capacity (Rushton, 1992), then this fact alone might explain (0.5 SD)(0.64)(0.4) = 0.13 SD of the brain size decrease, leaving 0.63 SD (57 cm3) not explained.

Perhaps the remaining shrinkage can be explained by a genetic drop in muscle mass that paralleled the drop in genetic height, but until ancient DNA studies explore SNPs associated with lean body mass, this remains speculation.

Given the 0.4 correlation between IQ and brain size (Jensen 1998)(Gignac & Bates, 2017), this would predict an IQ loss 0.4(0.63 SD) = 0.25 SD or 4 IQ points since the Upper Paleolithic, suggesting Cro-Magnon would have scored an impressive IQ 104 if raised in today’s America!

Genetic education predicts Cro-Magnon had an IQ of 89

Although brain size may have decreased in Europe by as much as 0.63 SD (after adjusting for body size), polygenic education scores (EA3 PGS) seem to have increased from what looks like -1.63 in Upper Paleolithic Europe type areas, to what looks like about -0.2 in Medieval England to about +0.2 in contemporary England (Piffer & Kirkegaard, 2024) for a total increase of about 1.83 SD since the Upper Paleolithic. Given a correlation of 0.4 between IQ and polygenic education scores (Pumpkin Person, 2024), this suggests a gain of 0.4(1.83 SD) = 0.73 SD since the Upper Paleolithic (11 IQ points), suggesting Cro-Magnon would have scored IQ 89 if raised in today’s America.

Indeed when I recently asked Peter Frost what their IQs would be if reared in today’s America, he guessed “high 80s”:

Combining brain size with genetic education predicts Cro-Magon had an IQ of 93

If brain size predicts Cro-Magnons have an IQ of 104 (if raised in today’s America) and genetic education level predicts an IQ of 89, and there’s no a priori reason to think one prediction is more valid than the other, then the only reasonable solution is to predict their IQs based on both variables.

The multiple regression equation predicting IQ from brain size and genetic education is:

Phenotypic IQ gap = 0.37(phenotypic brain size gap) + 0.37(genetic education gap) (Pumpkin Person, 2024).

When this formula was tested on the 15 point black-white IQ gap, it accounted for an incredible 13 of the 15 points! (Pumpkin Person, 2024).

Now applying it on the gap between today’s U.S. whites and Cro-Magnon man:

Phenotypic IQ gap = 0.37(+0.63 SD) + 0.37(-1.83 SD)

Phenotypic IQ gap = +0.23 SD – 0.68 SD

Phenotypic IQ gap = -0.45 SD

0.45 SD = 7 IQ points and is equivalent in SD units to a one inch increase in within sex height over 40,000 years. Kind of trivial. On a scale where today’s U.S. whites scores 100, Cro-Magnon would have scored IQ 93, consistent with the sophistication of their drawings; when I objectively scored these on the draw-a-man IQ test, they clocked in at IQ 90, though the sample size was tiny (n = 2).

Although some evidence suggests adaptive evolution increased ten thousand percent in the last 40,000 years (Hawks et al, 2007). Europe only gaining 7 IQ points in 40,000 years suggests evolution more or less ended in the stone age, consistent with the punctuated equilibrium model. This is consistent with the emergence of brain genes peaking 55,000 years ago (Libedinsky et al, 2023).

Richard Klein states:

What happened 40,000 or 50,000 years ago was the last major change in the genotype. At least the last major biological change. Evolution continues, but the evolution that’s involved in making us capable of wielding this vast variety of cultures–that probably stopped around 40,000 or 50,000 years ago and there’s been no essential change since.

Stephen Jay Gould agreed , famously stating:

There has been no biological change in humans in 40,000 or 50,000 years. Everything we call culture and civilization we’ve built with the same body and brain.