When I was a child, I didn’t understand that adults were more intelligent than children.  I thought adults just seemed smarter because they had more experience, but I didn’t realize there were biological changes in the brain that made them smarter.

Similarly there are some anthropologists like Sally McBrearty and Alison Brooks who argue that late stone age humans were just as smart as modern people, they just didn’t have as much time to accumulate culture, since our species was very young then.

This begs the question, since cultural evolution happens so much faster than biological evolution, how do we know when cultural progress reflects biological progress?

Most kids don’t study calculus until their later teens.  Is this because they’re not biologically ready until the brain approaches adulthood, or they simply haven’t had time to acquire the prerequisite knowledge?

Similarly representational art does not appear before the upper paleolithic?  Was this because our species wasn’t biologically ready, or not culturally ready?

Perhaps one way to tell is to look at the growth curve.  If knowledge or culture is progressing gradually in a person or our species, there’s no reason to suspect it’s anything more than cultural progress, but if the growth suddenly starts accelerating, then maybe cultural has had some help from biology.

For example, after 150,000 long  years of being confined to Africa, and being just one of several homo species on Earth, anatomically modern humans suddenly colonized six other continents,  created representational art, and replaced all other Homo species, in just 40,000 years.  This was such a massive change in our trajectory that scientists like Richard Klein think it must have been a biological leap in evolution, stating:

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.

Mitchell Leslie writes:

Forget about the construction of the first cities or the introduction of the internal combustion engine. The revolution that made the biggest difference occurred on the savanna of East Africa roughly 45,000 years ago, Klein and others maintain.

Stephen Jay Gould agreed with Klein, 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

However is the Upper Paleolithic Revolution really that much more dramatic than other revolutions that have since followed it?  Since cultural change is hard to judge, perhaps the most objective measure of humanity’s progress is population size.

It took us 200,000 years to reach a population size of 1 billion people,  and yet in just the last few centuries we’ve hit 7 billion!  That seems like a much bigger revolution than the Upper Paleolithic.  The Upper Paleolithic may have been when modern humans left Africa, but the industrial revolution is when humans left the Earth!

So why do people like Richard Klein invoke a massive brain mutation to explain the Upper Paleolithic, but feel no genetic explanation is needed for the industrial revolution?  Is this just political correctness or was the Upper Paleolithic genuinely in a class of its own?

I’m skeptical that a genetic mutation caused either, but just as biological evolution happens in sudden growth spurts (punctuated equilibrium model), perhaps cultural evolution does the same.

Here’s Klein discussing his views: