The Incredible Shrinking Brain

I like to have fun on Sundays, and today is no exception. At the library, I stumbled upon a thought-provoking article in the September, 2010 issue of the popular science magazine Discover. Called The Incredible Shrinking Brain, this article gets right to the point.

John Hawks is in the middle of explaining his research on human evolution when he drops a bombshell. Running down a list of changes that have occurred in our skeleton and skull since the Stone Age, the University of Wisconsin anthropologist nonchalantly adds, “And it’s also clear the brain has been shrinking.”

“Shrinking?” I ask. “I thought it was getting larger.” The whole ascent-of-man thing.

“That was true for 2 million years of our evolution,” Hawks says. “but there has been a reversal.”

He rattles off some dismaying numbers: Over the past 20,000 years, the average volume of the human male brain has decreased from 1,500 cubic centimeters to 1,350 cc, losing a chunk the size of a tennis ball. The female brain has shrunk by about the same proportion. “I’d call that major downsizing in an evolutionary eyeblink,” he says. “This happened in China, Europe, Africa – everywhere we look.”

If our brain keeps dwindling at that rate over the next 20,000 years, it will start to approach the size found in Homo erectus, a relative that lived half a million years ago and had a brain volume of only 1,100 cc. Possibly owing to said shrinkage, it takes me a while to catch on. “Are you saying we’re getting dumber?” I ask.

Hawks, a bearish man with rounded features and a jovial disposition, looks at me with an amused expression. “It certainly gives you a different perspective on the advantage of a big brain,” he says.

For me, it doesn't get any better than this. Are you saying we're getting dumber? I don't want to be culture-centric, but it sure does explain a lot of what we observe everyday in the United States. But of course that doesn't apply here, for it appears the brain has been shrinking for the last 20,000 years, not just recently in Washington D.C. or Anytown, U.S.A, but everywhere Homo sapiens ("wise man") lives and breathes.

It was thought that this might be simply due to a reduction in body size. Thus the size of the brain, proportionally speaking, is the same in modern people as it was in Cro-Magnons. This is called our Encephalization Quotient (EQ).

But the routine dismissal [of this shrinking brain trend] is not as weird as it seems at first blush, Stringer suggests, due to the issue of scaling. “As a general rule,” he says, “the more meat on your bones, the more brain you need to control massive muscle blocks.” An elephant brain, for instance, can weigh four times as much as a human’s. Scaling is also why nobody seems too surprised by the large brains of the Neanderthals, the burly hominids that died out about 30,000 years ago.

The Homo sapiens with the biggest brains lived 20,000 to 30,000 years ago in Europe. Called the Cro-Magnons, they had barrel chests and huge, jutting jaws with enormous teeth. Consequently, their large brains have often been attributed to brawniness rather than brilliance. In support of that claim, one widely cited study found that the ratio of brain volume to body mass – commonly referred to as the encephalization quotient, or EQ – was the same for Cro-Magnons as it is for us. On that basis, Stringer says, our ancestors were presumed to have the same raw cognitive horsepower.

Click to enlarge. Note that a Log/Log scale is used on the left, meaning that the difference between a human and a baboon or a wolf is much greater than it might appear at a glance. I've provided a simplified view on the right. At no point during the Phanerozoic Eon (543 million years ago to the present) did an animal with such a disproportionally large brain appear on Earth.

 Unfortunately, the EQ explanation of the shrinking brain problem does not hold up.

Now many anthropologists are rethinking the equation. For one thing, it is no longer clear that EQs flatlined back in the Stone Age. Recent studies of human fossils suggest the brain shrank more quickly than the body in near-modern times. More important, analysis of the genome casts doubt on the notion that modern humans are simply daintier but otherwise identical versions of our ancestors, right down to how we think and feel.

Over the very period that the brain shrank, our DNA accumulated numerous adaptive mutations related to brain development and neurotransmitter systems – an indication that even as the organ got smaller, its inner workings changed. The impact of these mutations remains uncertain, but many scientists say it is plausible that our temperament or reasoning abilities shifted as a result.

It is plausible that our temperament or reasoning have shifted. Think about that. The writer Kathleen McAuliffe offers up three theories to explain what that shift means. Of the three, only two are worth considering. The third, the "we use our brains more efficiently and are smarter as a result" theory can be dismissed out of hand. This view, taken by John Hawks, who was quoted at the top, seems to be based on obligatory, delusional optimism. There is has no real evidence to support it, it depends on a set of improbable positive genetic mutations having occurred, and is incompatible with that idea that proportionally bigger brains imply greater intelligence (the EQ itself). That leaves us with the other two theories—humans are dumber or humans are tamer. Both have merit.

Dumbing Down — The Idiocracy Theory

This quote says it all.

“You may not want to hear this,” says cognitive scientist David Geary of the University of Missouri, “but I think the best explanation for our brain size is the idiocracy theory.” Geary is referring to the eponymous film by Mike Judge about an ordinary guy who becomes involved in a hibernation experiment at the dawn of the 21st century. When he wakes up five hundred years later, he is easily the smartest person on the dumbed-down planet. “I think something a bit like that happened to us,” Geary says. In other words, idiocracy is where we are at now.

A recent study he conducted with a colleague, Drew Bailey, led Geary to this. Bailey and Geary found population density did indeed track closely with brain size, but in a surprising way. When population numbers were low, as was the case for most of our evolution, the cranium kept getting bigger. But as population went from sparse to dense in a given area, cranial size declined, highlighted by a sudden 3 to 4 percent drop in EQ starting around 15,000 to 10,000 years ago. “We saw that trend in Europe, China, Africa, Malaysia – every – where we looked,” Geary says.

The observation led the researchers to a radical conclusion: As complex societies emerged, the brain became smaller because people did not have to be as smart to stay alive. As Geary explains, individuals who would not have been able to survive by their wits alone could scrape by with the help of others – supported, as it were, by the first social safety nets.

Makes sense to me. Certainly the docile idiots we find in contemporary America could not survive 5 minutes as hunter-gatherers, who would no doubt ask "who are these dummies?" before kicking them out of the group because they were so clearly a severe impediment to the group's survival.

A Tamer Breed Of Humans — The "Sheeple" Theory

Harvard anthropologist Richard Wrangham is the leading proponent of the theory that humans have become more domesticated. Think cows or sheep. Sheeple!

Other researchers think many of their colleagues are barking up the wrong tree with their focus on intelligence as the key to the riddle of our disappearing gray matter. What may have caused the trend instead, they argue, is selection against aggression. In essence, we domesticated ourselves, according to Richard Wrangham, a primatologist at Harvard University and a leading proponent of this view.

Some 30 animals have been domesticated, he notes, and in the process every one of them has lost brain volume – typically a 10 to 15 percent reduction compared with their wild progenitors. Domesticated animals also have more gracile builds, smaller teeth, flatter faces, a more striking range of coloration and hair types – and, in many breed, floppy ears and curly tails. Except for those last two traits, the domesticated breeds sound a lot like us.

“When you select against aggression, you get some surprising traits that come along with it,” Wrangham says. “My suspicion is that the easiest way for natural selection to reduce aggressiveness is to favor those individuals whose brains develop relatively slowly in relation to their bodies.” When fully grown, such an animal does not display as much aggression because it has a more juvenile brain, which tends to be less aggressive than that of an adult. “This is a very easy target for natural selection,” Wrangham argues, because it probably does not depend on numerous mutations but rather on the tweaking of one or two regulatory genes that determine the timing of a whole cascade of developmental events. For that reason, he says, “it happens consistently.” The result, he believes, is an adult possessing a suite of juvenile characteristics, including a very different temperament.

Unfortunately, the"evidence" Wrangham uses to support this view makes little sense, at least to me. Here's an example where Wrangham is talking about our increasing "peacefulness" (non-aggressiveness) as a species.

“The story written in our bones is that we look more and more peaceful over the last 50,000 years,” Wrangham says. And that is not all. If he is correct, domestication has also transformed our cognitive style...

For more insight, [Wrangham's former student] Brian Hare is now studying other primates, notably bonobos. He tells me he suspects that these great apes are domesticated chimps...

Hare thinks bonobos became domesticated by occupying an ecological niche that favored selection for less aggressive tendencies. That niche, he says, offered more abundant sources of nutrition, so a habit of fighting over meals became less important to survival. From that lineage came the bonobos, highly cooperative primates known for their peaceful ways.

[My note: Yes, humans are just like bonobos—peaceful and cooperative ]

Both Wrangham and Hare see parallels between bonobo development and our own. Our self-domestication, they think, may hold the key to our species’s extraordinary motivation to cooperate and communicate – arguably the twin pillars supporting the whole of our civilization.

All I can say about this silly view is that if we're more "peaceful" now than we were 50,000 years ago, I certainly wouldn't want to run into a gang of paleolithic humans. If we had more broken bones then, surely it was due to hunting injuries, or the other pitfalls of the daily life of hunter-gatherers, not our more warlike nature in the paleolithic. In fact, non-delusional anthropologists think we became less peaceful after about 10,000 years ago. And why? Because with agriculture and the domestication of animals comes surplus, and with surplus comes wealth, specialization and cities. In short, for the first time in human history, there was stuff to steal.

Finally, we should not forget that it is "big men" and nation-states which wage wars. In short, the elites.

The Meaning Of It All

In the past I've said that Homo sapiens is a species, so what you see is what you get, which means don't expect to see significant changes in human behavior even as our problems mount. Each new generation is basically the same as the last, excluding trivial cultural differences.

However, perhaps I was wrong to exclude the possibility of physical/cognitive changes which are making the human situation even worse than it appears to intelligent, conscious people today. In fact, human beings seems to be both dumber and tamer than they were even 100 years ago. And considering Americans, it appears that they are much dumber and tamer than they were a mere 30 years ago. W was elected president of the United States—twice! (Maybe) How dumb was that? Just turn on the TV and watch WWE "Smackdown" for a while. If that's not Idiocracy, I don't know what is.

The American Idiocracy has come about too quickly to be due to evolutionary change, but it sure looks like we were "set up" to be in this increasingly grim situation over the last 10 thousand years. 

The "domestication" (we are tamer) theory can be saved by considering surplus, which I mentionedabove. In hierarchical societies, like all human societies (excluding vestigial hunter-gatherers or nomadic herders) since the invention of agriculture and domestication of animals, a very large majority of people live at the bottom of the pyramid, with only a relatively few, more aggressive people at the top.

If brain sizes (EQ) on average have been falling, it is not surprising because docile worker bees (called "consumers" in the U.S.) don't need such large brains to survive. And large brains are, from an energy consumption standpoint, very expensive. Which is why it is a total mystery as to why this trait evolved in our species in the first place. Adequate daily nutrition for all but 1 of the 7 billion people on Earth is not yet a problem, but brain size decreased over many thousands of years. Obtaining adequate nutrition was a struggle for nearly all of that time, especially for those at the bottom of the pyramid.

So what is the meaning of it all? God only knows, but the best evidence available suggests that human societies will go downhill from here on out. For this and lots of other reasons I could mention, we might conclude that maybe the evolutionary experiment (or accident) which gave rise to us wasn't such a hot idea after all.

Bonus Video — from Mike Judge's Idiocracy. Don't worry about the glitch in the first few seconds.

 

Comments

[Diogenes]

Whoa - I love it here.
I missed that article (dammit) - thanks once again for helping me fill in so many cracks. They from my skull shrinking?
So often these days this song comes to mind - by Black Dub with Daniel Lanois and the late, great Chris Whitley's daughter Trixie:
http://www.youtube.com/watch?v=CKpV140x7HM&ob=av2e
Swing away...

[Diogenes]

Sorry - upon a second reading this "rang an alarm":
"...we might conclude that maybe the evolutionary experiment (or accident) which gave rise to us wasn't such a hot idea after all."
Had to reach back 40 years, but I used to read Koestler and this popped into my head:

"The disastrous history of our species indicates the futility of all attempts at a diagnosis which do not take into account the possibility that homo sapiens is a victim of one of evolution's countless mistakes." The Ghost in the Machine

I used that possibility as the basis for a paper required in applying for some scholarship or grant money back then.

I didn't get that money - go figure.

[Bob S.]

Yes but a 70 year old swam the English Channel and ninety-year olds write best sellers.
Use what you have and don't whine about it.

[Sunger]

Dave- thanks for keeping up this blog. I have been reading daily for several years and think that you are spot-on most of the time.

We are peak-oilers/enviros who have taken to the rurals about 15 years ago and have become partly self-sufficient and trying to become more so. Gardening, wood heat, practical skills, a good well w hand pump, no debt, lots of mountain hiking & physical work.

We have observed the dumming down of the USA first hand in my inlaws family. Once a good farming family, it has become a group of frothing at the mouth ultra-conservative catholics and extreme Foxnews junkies- a good family that has been wrecked. They now embrace ignorance and read nothing- with personal slogans such as "northern by birth- southern by choice". They advocate nuking the entire middle east. And respond with deep anger if anyone contradicts their deep ignorance- which they are deeply proud of. "You think you are smarter than us".

May Dog save us!

[Brian M]

Interestingly, if the theory is correct, then if the decline of industrial society results in a) lower populations, b) less specialization, c)greater need to fend for one's own survival, it would seem to imply that those circumstances might mirror the older evolutionary conditions and might be expected to result again in increasing brain size.

So, history goes like this... grow brain, get smart enough to specialize, shrink brain, discover one-time bonanza of cheap energy, specialize and overpopulate into decline, fight for survival, grow brain.... whoops!, no more fossil fuels... well, at least our far-future decedents will have bigger brains.

They will likely need them.

[ALWYN]

From: "alwyn weiss"
To:
Subject: Brain Shrinkage
Date: December 4, 2011 12:54 PM

Sir a factor of importance is food.We are a herbivore by biology.Humans would eat mostly vegetations and some usually raw meat(big things and small things clams en bugs).hard to avoid vita c intake.Cook raw stuff vita c en enzymes go down.With grains you can spout them or eat early green stuff excellent food.Cook grain and quality way down(porrigde).Bread can be made from sprouted grain or ground kernels(flour) so a decline and a big decline.In modern era the pure "foodstuff" of little value.The four pure whites white flour,white water(alcohol),white sugar and white salt.Sea salt has many mineral in it,white salt is pure with some inadequate iodine added.Altogether towards raw better quality the other way is weak stupid shepple.The drug companies wont save us and high iol prices will guarantee push comes to shove and that is right now.The truth shall set you free. Alwyn

[S P]

I believe that up until industrial civilization really got going (early to mid 20th century), any dysgenic effects of agriculture or large populations were offset by deaths due to disease, famine, war, migration etc.

It's really only during the 20th century that we have a whole lot of stupid people (not to mention physically infirm, extreme elderly, etc.) running around. A graph of human population growth confirms this. The energy from fossil fuels tricks us into believing all these people can be supported.

Don't worry, we are quickly returning to a world where only the strong and intelligent are going to make it.

[Xraymike79]

And we are the only animal whose brain shrinks as they age...

"Human brains shrink as people grow old, unlike even our closest animal relative, says a new study in the Proceedings of the National Academy of Sciences that highlights what researchers call the unique character of human aging.
The human brain normally can shrink up to 15% as it ages, a change linked to dementia, poor memory and depression. Until now, researchers had assumed this gradual brain loss in later years was universal among primates.

But in the first direct comparison of humans to chimpanzees, a brain-scanning team led by George Washington University anthropologist Chet Sherwood found that chimpanzees don't experience such brain loss. From that, researchers concluded that only people are afflicted by this oddity of longevity.

"We are very weird animals," said Emory University anthropologist Todd Preuss at the Yerkes National Primate Research Center in Atlanta, who wasn't involved in the study...."
http://online.wsj.com/article/SB10001424053111903999904576468224286877908.html

[Jersey Patriot]

There is some question about how violent hunter-gatherer societies were. Steven Pinker has analyzed violence rates among modern industrial societies and among horticulturalists, and he concludes that violence has dropped a lot. Before anyone asks, yes, he includes World War II, the Holocaust, Iraq, Rwanda, the Drug War, etc.

However, there isn't much good data about actual hunter-gatherers. There seems to be some evidence that violence was high, but no one's sure if it was human violence or accidents or fights with animals. Horticulturalists move frequently, but are still tied to land while their food grows. Hunter-gatherers can move whenever they want, which makes avoiding violence a lot easier.

[Shirley]

Food for thought, without a doubt. Of course, I was waiting for the "Idiocracy" reference and wasn't disappointed. Thanks for the clip, too :)

A smart and, dare I say it, prescient movie. If you haven't seen it yet, do so as soon as you can: hysterically funny, yet at the same time, witheringly spot-on.