Researchers link human skull size and climate

maybe its simpler

bigger head = more hair = easier to cope with the cold.

@Peter W

Bigger head means more surface area to lose heat, and I'd suspect that the amount of heat retained by the additional hair-covered surface is NOT equitable to the amount of head LOST by the additional radiating surface.

Utter bollocks but still plausible

First, all modern humans come from a single tight lineage no more than 100k-150k years old. Any skulls that predate the exodus of homo sapiens sapiens from Africa are irrelevant.

Second, the driver for human brain size is the need for social skills; humans being above all successful because they can construct large and complex societies, through pure brain power. It's a safe assumption that skull size follows brain size, with thickness of the skull correlating to the level of violence in the society, and overall skull size limited by the technical considerations of the human birth canal.

Lastly, the driver for human expansion out of Africa probably *was* climate change, so in a very indirect way climate change could be seen as the cause of larger skulls, but it's really very stupid of the researchers to confuse correlation with causation.

Surface area vs. volume

I always thought that as as sphere got larger, the surface area per unit volume decreased.

As I see it, it comes down to heat dissipation - a larger skull has less surface area relative to the volume of brain matter within it, which means in a hot environment there would come a point where the brain couldn't be cooled adequately, and this would form a limiting factor.

If the air is cooler then more heat can be dissipated as the thermal gradient vs the head is higher, which means the upper volume limit changes and larger brains/heads become viable.

Beyond a certain point I would guess that cooling isn't as much of a problem as retaining heat, and this could have other impacts eg. need for more hair - plus it could drive even larger growth just to keep the volume/area relationship low.

This of course is what engineering suggests as the simple & obvious explanation - differing environmental challenges leading to a requirement for a larger brain doesn't seem quite so elegant, but thermodynamics probably isn't a strong point for biologists.

Heat Loss

Anyone who knows the tinyest bit about outdoor survival knows what 90% of your bodyheat is lost through your head, so you would have thought a smaller head would have become predominent as big headed individuals died of exposure in harsh conditions...?

The Religion of Climate

Yeesh! What claptrap.

Let me repeat this slowly for the comprehension-impaired:

Correlation does not mean causation.

There it is, simple, elegant and plain.

To restate that self-evident axiom, causal relationships can be considered a subset of correlative relationships, meaning of course, that variables can be correlated, even correlated tightly, without one of the variables having a direct causative effect on the other.

To illustrate, one can say that virtually 100% of humans who are addicted to heroin have used dairy products. That amounts to a correlation so close to 1 as to be indistinguishable from 1. And yet, despite the strong correlation, there is little evidence to support the hypothesis that dairy product use causes heroin addiction. Indeed, there are bodies of knowledge that support genetic, behavioural, and socio-economic causes of said addiction.

Brain case size and temperature might indeed share a causal relationship, but nothing presented in this synopsis would remotely support that hypothesis. What controls did the researchers use to isolate the effects of temperature change from the potential impacts other variables had on the outcome of brain case capacity?

Until there is something a bit more definite to report, this appears to be just one more instance of the result of speculative research finding its way into the ideological and polemic debate on climate.

Did some dimbulb in the communication department at the University of Albany make the connection that anything related to climate makes for "hot press"? Or is it a matter that some bored science reporter for some unamed pub has seized on this item as a means for fulfilling this week's quota of column inches? Or could it be a matter of some editor under pressure from his publisher to drive sales by ramping up the hype on climate change decided to publish the story?

Whatever the case may be, it sure isn't science.

Global Warming

So does this mean we can blame global warming for the poor performance of our students on standardized testing?

Back to front.

<i>Anyone who knows the tinyest bit about outdoor survival knows what 90% of your bodyheat is lost through your head, so you would have thought a smaller head would have become predominent as big headed individuals died of exposure in harsh conditions...?</i>

You have it backwards. As a previous poster pointed out, relative surface area decreases as volume increases. My mathematics isn't what it used to be but I believe this is because the surface area increases by the square of the radius while the volume increases by the cube. Or something. Whatever it is, a larger head means that less heat is lost overall.

For the record, the size of the brain does have an effect on intelligence, simply by virtue of the fact that a bigger brain generally means more synapses. Given that the size variance of human brains is very low it's likely any effect will be lost in teh noise of general IQ variance anyway (big headed idiots abound, whilst the alan sugars of this world get by quite nicely with their tiny, tiny heads) but when you compare a human to an ape, the differences become more obvious. Apes, while intelligent, are not as smart as people and that's down to the size of their brains.

The rule doesn't appear hold in all cases, of course. Blue whales have the largest brains on the planet. How smart are they? Actually we don't know... elephants brains are much larger than ours too, but you wouldn't claim they're einstein. Then again, how can you test such a thing given the limitations our nature places on our comprehension? How do you design an IQ test for an elephant?

Logistics of coping

One of my heroes, Otto Jespersen, suggested that a problem is best canvassed from all sides. One approach not yet noted in the comments is the need for a larger brain to handle the 'logistics' of coping with climate extremes. Much like the argument that complex social relationships required larger brains it can be argued that temperate climates require a larger brain to cope with maintaining a healthy body temperature over a broad, seasonal climate change.

If wide temperature variations promote bigger brains to handle the logistics then peoples of temperate climates might show increased brain size compared to people of extreme but less fluctuating climates. Just a thought, but it's worth noting I once attempted to develop a "fat-assed" theory of increased brain size in our species by postulating our big brains evolved as a counter weight allowing us to walk upright. In light of our plight seeing our brains as big ass ballast seems fitting.

The Bigger The Warmer, etc etc...

Physiologically the larger head size decreases the surface to content ratio, thus keeping the internal temperature warmer. You really need to stop running with the thinkers pal. Please go live in the tropics. I am so sick of lunch break pontificators who vent their liberal programming taking shots at all things "Us" while seeking desperately to embrace the "Other". People are different, respect it and work with it! Differences make this world interesting. You'd prefer to homogenize everything (and I do mean everything) so you reflexively deny and rationalize instead, it's getting old. If you want to make the world a better place drop the aloofness and patronizing, (it's downright embarrassing coming from people like you). Has it occured to you how many people will go contrary to messages presented in that pompous manner, even sensible messages like global warming? Either you want to improve the world or you want to play passive aggressive, games- judgemental and superior posturing to impress the ladies with your clarity and restraint, but it strikes women, more and more, as simply patheic posturing and parroting as compensation for not having any conviction in your self generated observations...

Speaking of Self-Appointed...

"Either you want to improve the world or you want to play passive aggressive, games- judgemental and superior posturing to impress the ladies with your clarity and restraint, but it strikes women, more and more, as simply patheic posturing and parroting as compensation for not having any conviction in your self generated observations..."

Speaking of tiresome isn't this rant just a bit 1980's feminist. Letting a discussion devolve into personally-driven gender issues and screed doesn't speak well of your ability to make a cogent point. I did appreciate, however, the subtle irony of your lapse into precisely those behaviours against which you rail - judgmentalism, posturing, parroting, self-generated observations. Nice touch.

Colder climate = larger prey

I was fortunate enough to spend some time studying zooarchaeology - at least enough to be introduced to the viewpoint that the climate affects the entire ecosystem, which in turn, affects humans in the region.

While I don't think discussions regarding heat retention are misguided, I think they should perhaps be expanded in their scope:

animals further from the equator tended to be considerably larger - particularly during the ice ages.

It goes without saying that it takes far more coordination (individual and social) to create the tools and strategize for a wooly mammoth mammoth hunt than many of the large birds, fish, rodents, and even herd animals that dominated the equatorial zone.

Just a thought.

What is head size for?

AFAIK, there is no proof that "intelligence" varies with distance from the equator. Equally, there is no evidence that "intelligence" varies with brain size (for "normal" brains). If there were, I'm sure we'd have heard about it by now :-)

Rather than assuming that distance from the equator allowed brains to grow to a more "productive" size, we should consider what other eveloutionary benefits might arise from moving to a cooler climate. I can think of one straight off: plumbing.

The brain is a very energy-intensive and blood-intensive organ. A larger head in a hot climate will presumably absorb more heat, which is inefficient for the body as a whole and the brain in particular (cheetahs can only run at top speed for a few seconds because their brains can overheat and they can pass out). By adapting the brain's plumbing to a cooler climate, evolution is making sure that growing a head is as simple as necessary (why waste effort - and risk failures - by fitting the plumbing into as small a space as possible?) and giving the body - and the brain in particular - another way to cool down.

Just because mankind's "intelligence" has allowed it to survive and thrive, we assume that it is more important than any other bodily function; nature doesn't care and is far smarter than us!

I'm not a biologist, BTW - please feel free to point out any errors in my assumptions :-)

Small brain

Helps to explain the South (US)