I have long championed the view that intelligence is the mental ability to adapt: to take whatever situation you’re in, and turn it around to your advantage.  I fell in love with this definition because it unified the many parts of intelligence (verbal ability, spatial ability, Theory of Mind) into a single system, and because it placed intelligence at its rightful place at the pinnacle of evolution: for all animals have adaptations, but humans dominate, because our adaptation is the ability to adapt itself.

But the question becomes, why did humans become so uniquely intelligent?  The logical theory that I had always believed, and that Darwin himself believed, was that it was bipedalism. Once we started walking erect, we freed our hands up to make tools and this selected for intelligence, which allowed us to make more tools, which selected for even more intelligence.


And yet the fossil record shows intelligence did not immediately follow bipedalism.  Indeed our ape ancestors may have been bipedal for nearly four million without showing much of any evidence for increased brain size or intelligence.

Then only in about the last few million years did brain size suddenly TRIPLE.  How do we explain this?

Scholar Rick Potts argues that during the last few million or so years there was rapid climate change in Africa.  Massive droughts followed by massive wet periods followed by massive droughts.  Lakes would come and go in the blink of a geological eye.  One day it dawned on Potts that it wasn’t the particular environment that was selecting for intelligence, it was the constant CHANGE in environment.

And who thrives in a constantly changing environment?  Those who can adapt.

Of course every organism adapts to its environment, that’s the point of evolution, however most organisms adapt by changing their genes over many generations.  We also adapted by changing our genes, but we took it a step further: We were selected for genes that allowed us to change our BEHAVIOR, which allowed rapid instantaneous change, far outpacing slow genetic change.

Intelligence is just whatever mental abilities are needed to change your behavior as successfully as possible.  Those who couldn’t learn quickly and think creatively during rapid change died out, leaving bigger brained primates as the survivors.

As an HBDer, I have long believed that adapting to newer colder climates caused whites and Northeast Asians to evolve especially high intelligence,  but I had no idea that climate change in Africa was so key to the evolution of human intelligence itself.

This theory is discussed starting at the 40 minute mark in the below video: