Are brains shrinking to make us smarter?

Human brains have shrunk over the past 30,000 years, puzzling scientists
Photo illustration of a brain scan. Human brains have shrunk over the past 30,000 years, puzzling scientists who argue it is not a sign we are growing dumber but that evolution is making the key motor leaner and more efficient.

Human brains have shrunk over the past 30,000 years, puzzling scientists who argue it is not a sign we are growing dumber but that evolution is making the key motor leaner and more efficient.

The average size of modern humans -- the Homo sapiens -- has decreased about 10 percent during that period -- from 1,500 to 1,359 cubic centimeters, the size of a tennis ball.

Women's brains, which are smaller on average than those of men, have experienced an equivalent drop in size.

These measurements were taken using skulls found in Europe, the Middle East and Asia.

"I'd called that a major downsizing in an evolutionary eye blink," John Hawks of the University of Michigan told Discover magazine.

But other anthropologists note that brain shrinkage is not very surprising since the stronger and larger we are, the more we need to control this larger mass.

The Neanderthal, a cousin of the modern human who disappeared about 30 millennia ago for still unknown reasons, was far more massive and had a larger brain.

The Cro-Magnons who left cave paintings of large animals in the monumental Lascaux cave over 17,000 years ago were the Homo sapiens with the biggest brain. They were also stronger than their modern descendants.

Human brains have shrunk over the past 30,000 years
Human brains have shrunk over the past 30,000 years. The average size of modern humans -- the Homo sapiens -- has decreased about 10 percent during that period -- from 1,500 to 1,359 cubic centimeters, the size of a tennis ball.

Psychology professor David Geary of the University of Missouri said these traits were necessary to survive in a hostile environment.

He has studied the evolution of skull sizes 1.9 million to 10,000 years old as our ancestors and cousins lived in an increasingly complex .

Geary and his colleagues used population density as a measure of social complexity, with the hypothesis that the more humans are living closer together, the greater the exchanges between group, the division of labor and the rich and varied interactions between people.

They found that decreased as population density increased.

"As complex societies emerged, the brain became smaller because people did not have to be as smart to stay alive," Geary told AFP.

But the downsizing does not mean modern humans are dumber than their ancestors -- rather, they simply developed different, more sophisticated forms of intelligence, said Brian Hare, an assistant professor of anthropology at Duke University.

He noted that the same phenomenon can be observed in domestic animals compared to their wild counterparts.

So while huskies may have smaller brains than wolves, they are smarter and more sophisticated because they can understand human communicative gestures, behaving similarly to human children.

"Even though the chimps have a larger brain (than the bonobo, the closest extant relative to humans), and even though a wolf has a much larger brain than dogs, dogs are far more sophisticated, intelligent and flexible, so intelligence is not very well linked to size," Hare explained.

He said humans have characteristics from both the bonobo and chimpanzee, which is more aggressive and domineering.

"The chimpanzees are violent because they want power, they try to have control and power over others while bonobos are using violence to prevent one for dominating them," Hare continued.

"Humans are both chimps and bobos in their nature and the question is how can we release more bonobo and less chimp.

"I hope bonobos win... it will be better for everyone," he added.

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Feb 06, 2011
It's interesting that the average brain size seems to have decreased. However, this article is mostly not science; not something I blame on the scientists themselves, as they were probably just chatting casually with the reporter, but annoying nonetheless.

Feb 06, 2011
Well I'd think this si an accurate depiction and probably what would be selected for. One of the main limiting factors on cranial capacity is the female birth canal. Larger brains mean larger heads, larger heads would result in more difficult births. It's a reasonable mechanic, but I don't see how the observations support this abstract.

Feb 06, 2011
So is civilization created and sustained because humans have lost the intelligence to survive in the more arduous, varied, and "primitive" conditions that our ancestors faced?

Do modern humans need the dumbed-down world in which others do most kinds of work for us because we're no longer capable of learning that variety?

Well, then it's a good thing that our planetary leadership has so carefully plotted a practical, sustainable future for the population. Oh, wait...

Hmm. I know. Let's invent our intellectual superiors and successors who will have the wisdom to know and to tell shrunken-brained humanity what to do.

All hail our future robot overlords.

Feb 06, 2011
"Women's brains, which are smaller on average than those of men..." -So Borat was right?!!?

-Our brains need to shrink because unnatural evolution in a near-constant state of tribal warfare, forced them to grow beyond a sustainable state. They are far larger per average unit of body weight than most any other animal, and consume a disproportionate amount of resources.

They are fragile and prone to all manner of dysfunction caused by genetic defect, damage, and age. Their structure and configuration were never intended to grow this big or survive this long.

One need only consider the prevalence of significant disease and behavioral problems within the general population, and the wide range of intellectual capacity wholly absent in any other species, to conclude that that the human brain exists in an unnatural state; and therefore the process which produced it must also have been an unnatural one.

Feb 06, 2011
We need smaller, more stable and less damage-prone brains with increasing artificial augmentation. We can internalize communications devices and outsource memory and calculation which never worked very well for most of us.

Feb 06, 2011
This is purely anecdotal, but having some exposure to "gifted" children, I haven't noticed a significant difference in intellectual ability relative to cranial size. But it seems gifted kids may have a higher percentage of large cranium kids, as opposed to the general population.

And, research does show a slight corollary between brain size and intelligence:


And cranial size and growth in childhood:


But it's also been suggested there's a corollary between cranial growth/size and autism:


And then there's the ever perplexing problem of getting a "big-headed" opinion of yourself...

Feb 07, 2011
Brain size varies considerably among individuals in all species. The sizes referenced in this article are averages. In modern man, a larger brain size corresponds very weakly to being more or less intelligent, so there is no reason to believe that these observations mean much.

Feb 07, 2011
Certainly not. They are not shrinking to do anything. Rather, for some reason, they are shrinking. Important difference there.

Feb 07, 2011
Socialization breeds stupidity and so does freedom. Freedom protects the stupid and they reproduce as much as they can. If our brains are getting smaller, we aren't getting smarter. Proof is any rationalization to the contrary.

Feb 07, 2011
Looking at some of the comments is painful. If you can't type without making multiple spelling and grammatical mistakes in every sentence, you shouldn't be commenting on an article about brain size.

Feb 07, 2011
It's not the size, it's what you do with it that counts!

Okay, lame joke aside, I think there is truth to that. A more efficient and connected brain wiring, including between brain hemispheres (corpus callosum) will surely manifest in higher cognition and intelligence, with a lesser demand for real estate.

It's interesting that Homo floresiensis had a cranial capacity of only 420cc, but was capable of producing relatively sophisticated stone tools. It looks like their brain morphology was different to ours, so again, it seems important what you do with it, rather than absolute size alone.

Feb 07, 2011
"Women's brains, which are smaller on average than those of men..." -So Borat was right?!!?

Haha thats EXACTLY what i said when i read that

Feb 07, 2011
The article doesn't say if brain size reduction equates cranium size reduction. Any help? If the human skull is at the limit for the birth canal size for safe delivery then is a cranium reduction an example of evolution of our species to ensure we dont die out? I realise we have medical tech. such as caesareans, but our genes dont know that.

Feb 07, 2011
I could have told you the last 20 years it has decreased 20%. Hint:watch TV

Feb 07, 2011
If I loose weight that means I will get smarter as my brain/bodyweight ratio is better.
Brains are there too think.
And they are just the right size to do that task. Mother nature would not tolerate such an extravagant energy use as brains use without getting a good energy return on the energy investment.

So. Let us examine the assumptions.
1. We are a lot smarter than our ancestors. (Anyone read Herodotus "The Histories" recently? Worked out the circumference of the world from simple observations? Arrogant apes.)
2 We are a lot smarter than those dumb Neanderthals. (Anyone survived naked in the Tundra recently? Morons.)
3 Evolution has a "Natural direction towards greater encephalization." (Anyone watched daytime television recently?)

The answer is simple. We are getting dumber because it is easier to survive with Oil providing all your calories.
A bit like the Dodo bird loosing it's ability to fly in the absence of threats.

Feb 07, 2011
The human mind, which can only be imperfectly represented, as a model, by a evolving, multiply connected Riemannian surface function, is conformable to a progressively less imperfect understanding of the inherent negative entropy of the universe. This concept of mind is what the age of Descartes referred to as "soul." His attempt to locate a physical connection to the soul in the pineal gland was as wrong headed, so to speak, as this quite non-sensical quibbling over the brain's size and intelligence. It is a simple school boy mistake to equate size with morphological complexity.

Feb 07, 2011
Are people today really smarter than people of the past? As our brain size shrinks it seems our heads are getting bigger."The more we learn the less we know."

Feb 07, 2011
Intelligence is a constant.
The population is increasing.

Feb 07, 2011
There are more factors to intelligence than size. The amount of "white matter", i.e. the myelinated interconnects that allow different parts of the brain to work together is a critical component. They've found that more intelligent people tend to have better and faster interconnections, so that their brains work in a more integrated fashion.

Feb 07, 2011
I've seen it argued that brain size began to shrink with the development of agriculture.

The invention of agriculture marked a transition in diets: increasing quantities of low-protein/high-carb food, and decreasing quantities of meats. Since the brain is a protein- and energy-intensive organ, then the periodic famines caused by low-yield years would tend to select for smaller brain sizes (particularly among children.)

Generally speaking, carnivores tend to have greater brain/body size ratios than herbivores. They can afford larger brains, because their diet packs a bigger punch; the cost-benefit books balance out.

So to me it makes total sense that as humans became more herbivorous, their brains shrunk due to metabolic constraints.

Of course, with the advent of modern hi-tech civilization, this dynamic probably no longer applies (at least, not in the developed nations.) But we're probably just a few decades away from Kurzweil's "singularity", which makes it all moot anyway.

Feb 07, 2011
Then again, people commenting on morphology and complexity vs. size also have a point.

Personally, I boggle at the notion that a tiny little spider has enough intelligence in its microscopic little pinhead brain, not only to govern its fairly complex body and its various forms of locomotion including crawling on floors, walls, and ceilings, as well as jumping, but also to drive mating behaviors, stalk its prey, spin complex webs, defend its territory against other spiders, and evade larger predators. Or, take an ant and all the things an ant colony is able to accomplish (sure, much of it genetically/chemically coordinated, but it's the ridiculously tiny brains of individual ants that drive their individual behaviors!)

Makes me think insect brains (and other systems) are FAR more optimized than those of mammals, never mind humans. Makes sense: due to comparatively short life spans, insects have gone through far more generations than we and our ancestors, over evolutionary time.

Feb 08, 2011
This is what keeps the brain of the meat eaters big(at general there are some exeptions), not the gain of the energy from the meat.

I don't think you can trivially reject the energy argument. Both the energy boost from meat and outsmarting your prey are factors, likely with positive (or reinforcing) feedbacks.

Feb 08, 2011
1) I am uncertain that we have the data available to determine the relative intelligence of our ancestors. The requirements for survival 15,000+ years ago are far different than the requirements in our present environment. Considering the significant differences in survival requirements the equitable points upon which intelligence is graded would simply have to be biased.

2) Brain pan volume != intelligence, only volumetric capacity. We do not have access to actual humanoid brains from 15,000+ years ago to examine the folding or neurological structure. With no more than volumetric capacity as evidence I really don't see how any solid conclusions can be made concerning intellectual capacity.

I dare say that modern man would likely be fatally inept if required to live the life of someone 15,000 years ago. We periocally find evidence of ancient humans having skills far in advance of what we previously gave them credit. I wouldn't discount their intelligence.

Feb 08, 2011

You could say that predators need to be smarter than the prey. On the other hand, smarter predators would create selective pressure to evolve smarter prey. In other words, it would be survival of the smartest, on both sides. Of course, you're right that intelligence isn't everything until you cross a certain threshold (e.g. toward tool-making); for most animals their physical attributes and preferred food sources are just as, if not more important.
the brain size corelates with the mass(not fat but how robust you are), and not with the intelect.
It does correlate with mass, but the brain/body ratio is not a universal constant. It differs across species, and it is the species with higher average brain/body ratios that turn out to be the most intelligent.

However, it must of course matter how efficiently the brain's volume is being utilized. Since our big brains are nascent in evolutionary time, I'd expect them to be quite sub-optimally organized.

Feb 09, 2011
I am not completely studied on the area of brain anatomy, but from what I gathered from the post and what I have read previously, most seem to agree on the environment playing a major role in body composition, and we have some for and against the bigger head bigger brain. I look at it like this, I think the brains are getting smaller for two reasons, our bodies don't need mass anymore because society has placed rules to protect us rather than us physically protecting ourselves as our primal ancestors would have done. And second we might be smarter because of the availability of information, but when it comes to the science of it how many of the normal population can explain how something works. Carl Sagan said "We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology." Maybe thats why they are shrinking

Feb 13, 2011
be more bonobo??
thats a stupid statement
they have sex with their young??
i don't think we really want to aim to be like either of them.

Feb 13, 2011
I cant get you point, are you saing the rabit is smart(I am talking for intelect like what raven can do or monkey)? Escaping from the predator doesnt require any thinking, furst the senses spot the predator, then it run, the manuvers he is doing during this are innated instinkts, it has no time to study this!

Feb 13, 2011
I love how everyone here is arguing over animals vs intelligence and at the same time don't define what intelligence is.
Perfect example of how intelligent human beings really are.
I also love the comment about ants being really efficient. In that way ants are relatively extremely intelligent than humans.
I mean just look at our fuel cars, they are like 30% efficient? While we already have the knowledge for superiour cheap batteries and we dont use them. An electric car is alot more efficient, maybe 90%? And a plant that would burn fuel is alot more efficient than 30%.

Nah we human beings are stupid as .. rocks, actually more stupid than rocks. This article is a fine example.

Feb 13, 2011
I mean just look at our fuel cars, they are like 30% efficient? While we already have the knowledge for superiour cheap batteries and we dont use them. An electric car is alot more efficient, maybe 90%? And a plant that would burn fuel is alot more efficient than 30%.

Not entirely good for the planet though, the pirius is is a good example as it causes more environmental damage to the planet over its life that a new landrover discovery. And really its not that much more effecient, its just the fuel is coming from another damaging source in another place. So really yes we are stupid, we're taking the pollution out of the cities where we live and placing the pollution in the wild, where we grow our food. So now instead of inhaling it we'll be eating it

Feb 13, 2011
The prius is not an electric car. Its a hybrid car. Just because it has an electric motor doesnt make it an electric car.

Feb 13, 2011
And i have always know since day 1 of hearing about hybrid cars that they will be worse than combustion cars since it contains more parts. also the prius looks really heavy and bulky...

Feb 13, 2011
i hate that car with a passion since people will actually believe that they are helping the environment.
The heaviest part of the electric car is the batteries. Batteries are indeed bad for the environment, but thats where new battery technology comes in, to bad we have the knowledge but dont use it!

Feb 13, 2011
i hate that car with a passion since people will actually believe that they are helping the environment.
The heaviest part of the electric car is the batteries. Batteries are indeed bad for the environment, but thats where new battery technology comes in, to bad we have the knowledge but dont use it!
The Prius IS better for the environment. Generally, it gets all of its energy from the gasoline it burns. It just utilizes that energy more efficiently.

The new plug-in versions will use the grid to obtain some power. Grid energy is cleaner than gasoline. This is particularly true in regions where nuclear and renewable energy sources are prevalent.

As far as environmental damage, there is some additional mining required to obtain the materials for the batteries, but the batteries themselves are generally recyclable. The rest of the car is recycled as well (as has been the case in the materials industries, for generations).

Feb 13, 2011
Yeah and the recycling will cost alot of energy again, and the process is bad for environment anyway. We really need new battery tech, the battery we use now wear down quickly and dont have alot of charge/mass, for most cars its not a problem electric cars can have a bigger range/efficiency than combustion cars.
And can you post me real evidence that the prius actually is more efficient than normal combustion cars? Where does it get the energy from? And is this energy more than the weight of the extra parts? I dont think so. also the prius looks like a heavy car to me. Theres better electric cars out there. If everyone would use electric cars and energy plants combust the fuel it would be alot more efficient.

Feb 14, 2011
We are DEVO.

Feb 14, 2011
"Based on 45 long bones from maximally 14 males and 7 females, Neanderthals' height averages between 164 and 168 (males) resp. 152 to 156 cm (females). This height is indeed 12-14 cm lower than the height of post-WWII Europeans, but compared to Europeans some 20,000 or 100 years ago, it is practically identical or even slightly higher."

You can find plenty of info in the net, they were more robustly build, it is like with the dogs, short but robust dogs have big heads and more brain, and gods like afghan hound and gods from this sort have smaller heads, allso if you observ the modern human you will find the same thing, the head correlate with the robustness, not so much with the tallnes, as I mentioned before.

Feb 14, 2011
And actually the paralel with the dog can give you pretty much the answer, do the more brain (which is due to masivness)make the dog smarter, you will find there is no paralel, border coly and the pudel are cosidered most smart, they dont have big heads.

Feb 14, 2011
"Neanderthals were much more muscular than are modern humans - bulking about 30 percent more in weight. Both their skull (Harvati, 2003) and body morphology are different to archaic and modern H. sapiens morphology". Here what I found, the bigger brain is pretty much understandable with these 30 percent more mass.

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