Tuesday, September 22, 2009

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.

- Holly Dunsworth, guest blogger

Further Reading:

Race is a Four-Letter Word: The genesis of the concept by C. Loring Brace (2005)


EllenQ said...

Extremely thought provoking post Dr. Dunsworth! What strikes me most about Dawkins' comment is that the hypothesis that he meant to set forth was "Will we be more intelligent in 10ky?" but he didn't really answer that question either. He is saying that people who aren't as intelligent are the ones having more babies which is based entirely on his own view of what constitutes intelligence.

Dawkins is clearly a brilliant man, but is his kind of intelligence really the type that was selected for in our ancestors? Or is this modern, academic intelligence a byproduct of a more useful type of social intelligence or spacial intelligence that allowed our ancestors to live in increasingly complex social groups and to forage successfully for food? I would argue that if we define intelligence in terms of ability to survive in difficult situations, perhaps the most intelligent people are having the most kids.

I think we all know people who are considered brilliant by our standards but are socially dysfunctional and couldn't feed themselves if it weren't for frozen dinners.

Holly Dunsworth said...

*laughing out loud*

Jason Hodgson said...

Great post, Holly.

I don't find the idea that there may be between population variation in intelligence threatening. In fact I find it comforting in some ways. More comforting, in fact, than if there weren't between population differences and only within population variation. I'll explain why.

Though there are not human races, there are certainly between population differences in human groups. When I walk around New York I am tall. When I recently visited Amsterdam I was very short. I am the same height no matter where I'm standing. It is the populations that changed. Human genetic variation is undoubtedly structured geographically.

I think it the case that if there are population differences in intelligence it should not be very surprising. In fact, if there is heritable variation WITHIN a population and that variation is caused by MULTIPLE genetic loci then we should be surprised if there is NOT between population variation in the phenotype. The reason for this is the same as for why we can always detect genetic structure between populations when it exists with multiple polymorphic loci (but not always with a single locus). When you look at a single locus, a very slight differences in allele frequency between populations is not informative. However, when many such loci are used the very slight differences in frequency between populations mean haplotypes (combinations of alleles) become more and more likely in some populations than others. The more loci you look at the more statistical power you have to detect this haplotype structure. A recent paper was able to recover the village a person came from in Sardinia using half a million polymorphic nucleotides. ...Anthony Edwards provides a clear explanation of the power to detect population structure with multiple loci in a piece titled "Lewontin's fallacy".

Lots of variable traits are polygenic. There are lots of genes that effect height, skin color, etc. There has been a lot of effort to find genes that effect intelligence. The findings suggest that there is no normal genetic variant anywhere in the genome that has a large effect on intelligence. Instead, there are probably lots and lots and lots of variants that have tiny additive effects.

These are variable within populations. It would be shocking if there weren't slight differences in allele frequencies between populations. In aggregate this would necessarily result in phenotypic structure just as the slight differences in frequencies result in genetic structure.

The interesting thing about variation like this is that it is evolving neutrally (or near neutrally)! Natural selection eliminates variation. These loci are variable because it pretty much doesn't matter what variant you have at any one loci. There is no strong selection for or against any of them. Consequently their frequency within a population is a function of genetic drift. Genetic drift will randomly differentiate between populations. But this variation is irrelevant to the functioning of the organism as far as evolutionary fitness is concerned.

I find it comforting to think that if there is between population variation in intelligence, the variation is so slight and so functionally meaningless that evolution has turned a blind eye to it. We might think that intelligence is so important that natural selection strongly favors it, but within our species the null hypothesis that variation in intelligence is meaningless has certainly not been falsified.

Holly Dunsworth said...

Thanks Jason for your thoughtful thoughts!

I always get hung up on our inability to quantify "intelligence" and also to boil down the genetically controlled parts of whatever "intelligence" is from the environmental influences on it.

And I find comfort in there.

Unknown said...

Excellent commentary, Holly. Very interesting.

I'm often impressed by how the brain is always active (Just try to stop thinking for 10 seconds ... *fail*!). I've heard that 80 percent of our energy goes into maintaining brain function.

You're right about intelligence, there's IQ and EQ and so many other dimensions that we don't know quite what it is. Maybe a better overarching term would be "capability" though I don't presume to know how you would measure it, either. Dawkins' comment about brain size in evolution could be misconstrued and you're good pointing out why we must be more clear on that. The brain stopped getting bigger a long time ago, hmm. I wonder if that's when shared thought took off, launching memes (a la Dawkins), information, and concepts as the "next wave" of human evolution. Didn't need such big brains once we had language?

It's legitimate to wonder how different family sizes of different groups will affect humans overall, but I suspect it's more a matter of concentrating wealth than anything else. I think humans are so "capable" that, given the choice, we often buy more stuff instead of have more kids. I've read recently that upper middle class families are having more children than before, and ASFertility rates continue to fall in the developing world. Now I'm worried about the environmental effects of more rich people!

We do have to be careful not to misconstrued evolutionary processes so they encourage racism. That would be a pity and a shame and we must guard against it; thanks for making that important point so well.

Holly Dunsworth said...

Thanks Tintin! It is fascinating to think about how things took off cognitively and culturally.

Mong H Tan, PhD said...

RE: Dawkinsism is not a “misstep” -- It’s a self-denigrating “pseudoscience meme” or scientism par excellence of the 20th century, emanating from Oxford since the 1970s!?

Dawkins's misstep adds unfortunate credence to this pseudo-scientific nonsense.

Good catch, Holly! However, I thought that “misstep” is still an understatement for someone; especially for someone who is the world-renowned neo-Darwinist reductionist, and that is unequivocally Richard Dawkins (RD)!

Briefly, in my final analysis of RD’s lifetime’s works -- since the publication of his first reductionist book The Selfish Gene (1976) -- I came to conclude that RD is one of the foremost purveyors of scientism (as referenced above) or Dawkinsism of his own making at Oxford -- one that RD had had never paused to reexamine his own faulty reductionist theory of evolution; and one that he has had indeed aroused great intellectual and spiritual distresses, in both the scientific and religious communities since the publication of his 2006 anti-religious book The God Delusion -- as I recently characterized here: “Let's begin the Dialogue and Reconciliation of Science and Religion Now! -- RE: What's mind (or never mind)!? -- Deciphering idiosyncrasies of scientific/religious rationalism vs. neo-Darwinist/ID-creationist irrationalism, in science and philosophy today!?" (PhysForumEU; August 2).

Best wishes, Mong 9/23/9usct1:45p; practical science-philosophy critic; author "Decoding Scientism" and "Consciousness & the Subconscious" (works in progress since July 2007), Gods, Genes, Conscience (iUniverse; 2006) and Gods, Genes, Conscience: Global Dialogues Now (blogging avidly since 2006).

Unknown said...

Wait a moment please. Mong I see you have a bone to pick with Richard Dawkins. But please consider what he actually said here before you vilify him. He said that the human brain has grown in size (it has) and that size of brain is related to cleverness (in relation to body size, it is). And the only way it will continue growing is for large-brained people to have more children. That is also true, so long as those children survive through parenthood themselves.

His mistake, if I may, was to *equate* "cleverness" with large brains, because positive correlation there is just not very strong. Neanderthals had larger brains than we do, after all. And yet here we are, wala.

I'm not going to defend RD as he does a pretty good job representing himself. What's most unsettleing is not that he's off the mark; it troubles me a little that he's probably right.

Unknown said...

Oops, that reads badly. I don't mean he's right about brain size and cleverness. Holly was good pointing out that important mistake. I meant generally right in his perspective. :)