Evolution on the March

Last month, we had a couple of good discussions here about the nature of civilization and about the role of evolution in changing humans and human societies.

It's looking more and more like biological evolution could in fact be making a difference on a shorter time span than previously thought. From the BBC:

Researchers have found that the shape of the human skull has changed significantly over the past 650 years.

Modern people possess less prominent features but higher foreheads than our medieval ancestors.

Writing in the British Dental Journal, the team took careful measurements of groups of skulls spanning across 30 generations.

The scientists said the differences between past and present skull shapes were "striking". . .

The two principal differences discovered were that our ancestors had more prominent features, but their cranial vault -- the distance measured from the eyes to the top of the skull -- was smaller.

Dr Peter Rock, lead author of the study and director of orthodontistry at Birmingham University, told the BBC News website: "The astonishing finding is the increased cranial vault heights.

"The increase is very considerable. For example, the vault height of the plague skulls were 80mm, and the modern ones were 95mm -- that's in the order of 20% bigger, which is really rather a lot."

He suggests that the increase in size may be due to an increase in mental capacity over the ages.

So, does it seem plausible to you that humans today might be, say, 20% smarter than our medieval ancestors? Could that, if it's true, be a contributing factor to the explosion in scientific discovery, technological progress, and improved living conditions over the last half millennium?

Mike Treder

Tags: nanotechnology nanotech nano science technology ethics weblog blog

Comments

[Nato Welch]

So if selection pressure was supposed to explain this, what was it, exactly, that was killing off people with 80mm vault heights?

[Vinayagamoorthy]

I have read that Monkeys started becoming intelligent after playing with hands and handmade tools, which in turn lead to the increase in brain size. Similarly playing with science and technology might have increased the cranial vault height.

[Greg]

Maybe people with large heads had a larger chance of dying along with their mother during childbirth?

So if selection pressure was supposed to explain this, what was it, exactly, that was killing off people with 80mm vault heights?

Malnutrition?

Some have theorized that as the poor died off the poorer cousins of the rich filled their niche.

[Chris H]

Perhaps the larger size is due to better nutrition.

[Mike Doughty]

I think Chris H. is correct. Hasn't general human stature increased by about the same amount? Look at armor from the Middle Ages and see how small the average knight was; and these were the upper classes, who supposedly would have had the better nutrition of the time.

[Skyler]

Or, maybe better diets led to better growth in childhood?

[BlogDog]

Perhaps the study could have said, "Check out the big brain on Brad!"

[john]

I have always thought that Women with higher foreheads are more beautiful.

Large heads, and , ahem, other large things are attractive.

[Sarnac]

Merge the two explanations:

Better nutrition allows for larger people.

As nutrition improved (baby size increasing), smaller medieval mothers would be selected against (die during childbirth before having 2 or more kids alive)

Bigger females can give birth to babies with larger heads without dying.

The pelvic/birth-canal-size increasing-stature selection-pressure on females would also provide the genetics for the increased male stature over the same multi-century time-frame.

[Dr. Ellen]

Mike Doughty -- armor worn in battle gets trashed pretty rapidly, so a lot of the surviving armor was worn by the kids while they were still learning how to fight. A school uniform, as it were. (Just a general impression of possible size bias.)

[Russ Mitchell]

Indeed. In addition, Mike, Ellen, for much of the medieval period, people were *not* smaller. Real height and nutrition problems as we know them seem to be more an issue for the early-modern world and its chronic food shortages. While height has definitely increased, the super-runty folks we're used to thinking of are just as likely, if not more, to be 17th-century as 13th.

[sagl]

Be interesting to see if this has occurred in other societies as well; and to correlate with innovation in those societies.

[James wilson]

Ya. Clearly. Midevil man could not have been made to understand that global warming was a bad thing, or that it existed; that the civilized would invite the uncivilized into their homelands to blow them up; or that the planet would benifit greatly were homo-sapien to kindly just dissapear from it.
You've got to be really smart to understand these things.

[KRB]

The evolutionary argument does not necessarily entail a claim that the 80mm vault-height people were "killed off." Instead, it only requires that those with higher vault heights had greater reproductive success than those with lower heights -- not that those with lower heights had no reproductive success at all. One plausible explanation -- though not the only one -- is that the higher vault height is a reflection of intelligence and those with more intelligence had greater reproductive success than the less intelligent.

"So if selection pressure was supposed to explain this, what was it, exactly, that was killing off people with 80mm vault heights?"

[KRB]

The evolutionary argument does not necessarily entail a claim that the 80mm vault-height people were "killed off." Instead, it only requires that those with higher vault heights had greater reproductive success than those with lower heights -- not that those with lower heights had no reproductive success at all. One plausible explanation -- though not the only one -- is that the higher vault height is a reflection of intelligence and those with more intelligence had greater reproductive success than the less intelligent.

"So if selection pressure was supposed to explain this, what was it, exactly, that was killing off people with 80mm vault heights?"

[Pat Berry]

Turning off the italics (I hope).

[John]

People today are about 20% larger in every way than those living 600 years ago. A six footer was a giant in the 14th century. If cranial vault size was increasing faster than the overall size increase in the human body, then there might be something here.

[Patrick Brown]

Humanity is getting smarter on a shorter time scale than that - according to James Flynn: http://en.wikipedia.org/wiki/Flynn_effect.

The Flynn Effect shows increases in IQ scores on the order of 7 points per decade.

[lex]

Italiacto!

[Charlie]

John's comment is probably headed in the right direction. High foreheads considered to be more attractive would lead to more selection for that trait. The results become breeding rather than evolution. Breeding can make for rapid change as we've seen in our canine population.

Still, lower vaults likely wouldn't have been bred out. The question becomes how representative these 30 generations of skulls are.

Another possibility... fetal and newborn mammals undergo massive brain-cell die-offs. How the process tailors our makeup is poorly understood but has been postulated to account for the extremely rapid evolution of the Spanish wild cat to our domestic tabby, for example.

[RebeccaH]

There probably isn't one specific cause. Better nutrition, better hygiene and health overall, and brains that simply have to store more abstract information than ever before in human history.

[Svigor]

...But the races are still cognitively identical, because they haven't had enough time to differentiate...because...to say otherwise is heresy...

[Firus]

*You've got to be really smart to understand these things.*

But not to spell correctly?

[Kevin]

Huh, I didn't realize Phrenology was still considered a legitimate science! Besides, of COURSE we're smarter than out bug-eating middle age ancestors. How many of them knew how to program computers? Thought so.