My brain is no bigger than a caveman’s

Many people, including myself, consider Richard Dawkins to be well above average when it comes to intelligence.

So is the size of his brain above average too?

Not necessarily.

Nobody has discovered a way to use a person’s intelligence to predict their brain size and vice versa.

What’s more, all of our brains are no larger on average than those of half-million-year-old “archaic” humans - the kind of people who hunkered down in caves to rest between hunting expeditions or to hide from hungry saber-toothed cats.

In spite of these issues - in spite of it being impossible to use someone’s head size to predict their IQ score or even to predict whether they are simply above or below average in the intelligence department – so many of us mistakenly cling to the notion that that “smart” people have bigger brains than “stupid” people.

It’s partly evolution’s fault.

Evidence from the fossil record and from comparative anatomy of living species makes it clear. Along with body size, an increase in brain size is a common trend in many evolutionary lineages. Over the last two million years our lineage experienced an extreme increase in brain size. And although it has not been as pronounced in other lineages, encephalization has also occurred in apes, monkeys, elephants, whales, carnivores, birds, cephalopods, etc. Mother Nature certainly likes big brains, but she would never ramp up the growth of something so metabolically and developmentally expensive if there wasn’t a payoff. We assume this has something to do with brain function, or intelligence.

Even those who know little or nothing about evolution (or deny it happens all together) can make the connection. After all, our brain is where our intelligence lives and our brains are conspicuously large. We can do all sorts of wonderful things that other animals cannot, so of course our large brains play a role in that.

It is hard not to apply this logic to the variation that we see within our species. But we shouldn’t.

And neither should Richard Dawkins as seen in this recent interview…[start at minute 4]

What’s the big deal? What’s wrong with what he said? It sounds pretty reasonable. Aren’t I just reacting too sensitively to his use of the fact that less educated people have more children than highly educated ones? They do. He’s right. We shouldn't have to be politically correct about facts. I sound like a knee-jerk liberal. Okay okay.

The point here is not to bark about Dawkins potentially misspeaking. He may wish he had said things differently here, and Darwin knows that I wish that very thing after most teaching bouts.It’s just that his hypothetical future evolution scenario was supposed to clarify evolution for the public, but it only raised questions and further supported racist beliefs. Ambassadors of Evolution should be more careful.

Looking around the animal kingdom, it is clear that brain size is correlated to intelligence. Those animals with big brains are the most intelligent. Our common mistake lies in applying that observation to modern humans and towards understanding our current variation in brain size and intelligence.

Whatever drove human brains to achieve modern size about 500,000 years ago is something that unites us all. This is true regardless of our current variation. And this was a type of intelligence, which we all carry with us, that laid the groundwork for all the cognitive and cultural development that has occurred since.

So the development of art, farming, calculus, plastics, microchips, neurosurgery, crossword puzzles, etc… all that stuff (all of which is a big part of intelligence estimations and measures) has nothing to do with why our brains got big in the first place.

Of course intelligence varies between people. But if brain size and intelligence were linked in our species, wouldn’t we be able to spot an intelligent person just by looking at the size of their head? Wouldn’t NASA and Harvard measure heads just to keep their applicant pools in check? Wouldn’t women give up trying to compete with men who have bigger brains than us? Wouldn’t people who wear small hats give up their Jeopardy! or architect school ambitions or just never dream them up in the first place? Most of us already know, whether we realize it or not, that brain size and intelligence are not linked anymore in the hominin lineage.

Once we get past that, then we can ask a couple of really interesting questions.

What did Mother Nature find so fascinating about our brains 500,000 years ago? What kind of function was our brain providing in the middle Pleistocene that required it to be so big back then?

Stone tool technology - which is one of the few things that is preserved from this time period – steadily advanced and became more and more elaborate and complex during this phase of our evolution. So, invention and technological intelligence, which goes along with physical intelligence like manual dexterity, is a good explanation for our encephalization. Another strong hypothesis suggests that social networking was so utterly important to our survival and reproduction that only with a larger cortex could a person maneuver and compete within a large society full of other intelligent creatures. Political games, power struggles, relationship forming, relationship maintenance, and resource acquisition (e.g. cooperative foraging and hunting) may have all relied on a big social brain. Language was another likely brain size booster.

Given that the trend for increasing brain size began 2 million years ago and lasted for about 1.5 million years, why did it just stop in the Middle Pleistocene?

Maybe we had all the brain we needed. Look how far we’ve come with caveman-sized brains!

It’s also possible that this is as big as it gets: Metabolic and developmental constraints may prevent our brains from getting any bigger.

Okay, so Dawkins jumbled up the story of human brain size evolution and intelligence. Still, what’s the big deal? What part of it flirts with racist beliefs out there? If you look back into the history of science and pseudo-science, there is a long tradition of measuring heads in different human populations and a long history, which continues today, of concluding that some “races” have smaller brains than others. There is also a long-held belief that some races (which are historically grouped by geographic origin, skin color, language, and other cultural traits) are more intelligent than others. In both brain size and intelligence, guess who gets ranked lowest most often in these "studies"? Africans and people with African ancestry. So to determine if someone is intelligent, we might take into account skin color, nose shape, eye shape, and cultural factors like language and body adornment. Dawkins's misstep adds unfortunate credence to this pseudo-scientific nonsense.

One big confounder is that we know very little about what causes variation in human intelligence. We know that intelligence is not determined by genes alone, but that genes do play a role since they build the brain. Natural Selection could act on these genes and drive evolution, as Dawkins said. However, intelligence is much more than “good genes”. Something as simple (but often so hard to obtain in a crowded world) as good nutrition contributes greatly to neurological and cognitive development.Environment is another key factor. Stimulation, practice, learning, and discovery, along with a healthy diet, help children become mental gymnasts who can grow up to qualify for the intellectual Olympics. It seems to me that if we put the need for nutrition and education programs in terms like, “Granting all Americans the opportunity to be intelligent citizens,” there may be may be more taxpayer support.

As Ambassadors of Evolution, it is our duty to clarify for others what we know and what we don’t know about the evolution of the human brain and intelligence. Even more than the “aquatic ape” hypothesis, the evolution of intelligence is consistently the most popular topic in public and classroom discussions of human evolution, and yet is the most dangerous given our sordid history, but having this discussion holds the potential to improve the human experience.