Tall, to short, to tall (again) : Gene Expression

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Tall, to short, to tall (again) permlink

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Posted on: September 29, 2006 11:33 AM, by Razib Khan

Dienekes reports on a paper which chronicles the change height of "Europeans" over the last 20,000 years ago. Anthropologist Henry Harpending once told me that when the first modern humans arrived in European 40-30 thousand years ago they were as slim and towering as modern Nilotic peoples, in other words, they were evolutionary reflections of the African environment. But soon enough the nouveau Europeans shape shifted and developed a more robust physiognomy, with a reduction in median height. As you can see from the graph which I generated the Neolithic Revolution and the introduction of agriculture was the nadir of physical size, and undernourished reality of the farming cultures of Eurasia was a fact of life until the past century. But, note that even today Europeans are not as domineering in stature as they were 20,000 years ago. Humans have a tendency to view evolution as a progressive force, toward more complexity, size and intelligence. But we aren't sure that this is correct, not only were modern humans larger during the Ice Age, but the largest cranial capacities of any human population can be found among the Neandertals.

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Comments

re: we tend to view evolution as a progressive force towards greater complexity

I have often wondered how one "measures" complexity in this context, or, indeed, in any biological context. Is it quantifiable? Or is it a subjective category like "beauty"?

Posted by: Luke Lea | September 29, 2006 12:40 PM

Coincidentally, the skulls with the largest crania belonged to UP Homo Sapiens Sapiens (Barma Grande, Afalou bou Rhummel, etc.).

Posted by: Shogun | September 29, 2006 1:04 PM

I wonder if a similar pattern would emerge from the trend of bad breath over the same time period. I know you can check tooth decay, but that could be due to malnutrition, tooth-rotting foods, etc. I mean, the actual presence of microbes that would give one foul breath. You figure that since we were swamped with all sorts of new microbes after the agricultural transition, our breath likely became much more disgusting, only regaining our previous peak once fluoridated toothpaste and antiseptic mouthwash became common during the 20th C.

I only mention this b/c that's one thing people fixate on when watching Survivor -- "imagine how gross your breath would get!" But then all participants have spent decades colonized by germs that a real, pre-agricultural H-G wouldn't have experienced.

Plus, imagine the selective pressure bad breath imposes -- if a female had relatively unscented breath, even if not redolent, she probably would've enjoyed a fitness gain similar to a mildly attractive girl amidst a village stricken by smallpox. Such a girl would also probably have had nice teeth, but I think the "unscented breath" effect would contribute a fair share of unique variance.

Posted by: Agnostic | September 29, 2006 4:48 PM

Agnostic,

There was a TLC show about boot camps, and one of the anecdotes was about how no one noticed their fellow members' body odors during the several hours of gruelling excercise. Yet, once they showered and were heading to the canteen, a rival team returning from their excercise seemed to reek. The concept of "unscented" is highly relative. Fellow tribal folk whose bad breath was similar to yours due to similar diet would appear "unscented" whereas a rival tribe's deviant diet would make their odors foul.

Posted by: sic semper tyrannis | September 29, 2006 11:29 PM

Never thought about it before, but being tall helps dissipate heat, whereas being short helps retain heat -- surface area per unit mass. So malnutrition doesn't have to be the sole or even the primary cause, at least for the initial decline.

Ultimately you do have to explain the tall people that there are now, especially the tall, husky ones. Oddly enough, the Dutch are at the top of the last list I saw (comparing nations, that is, and excluding the Dinka.)

Posted by: John Emerson | September 30, 2006 9:11 AM

Dear Razib,

In reference specifically to your statement, "Humans have a tendency to view evolution as a progressive force, toward more complexity, size and intelligence..." I have to say I agree, and anything that helps dissolve the simplistic, "progressive" misapprehension of evolution is a good thing.

Perhaps proponents of Intelligent Design would reconsider their position if they understood more about the train they are climbing aboard -- for certainly an intelligent designer would evolve his toys to a plateau of excellence, rather than letting them skip and linger and meander around local ESS puddles all willy-nilly.

Also, very tall ancestors make me wonder about the origins of Niphilim stories.

Love,
Cheeseburger Brown

Posted by: Cheeseburger Brown | September 30, 2006 10:08 AM

surface area is key. northern europeans are tall, but not necessarily slender.

Posted by: razib | September 30, 2006 11:05 AM

Luke Lea: "I have often wondered how one "measures" complexity in this context, or, indeed, in any biological context. Is it quantifiable? Or is it a subjective category like "beauty"?"

I've pondered a similar question concerning evolutionary "progress". What if you could take sample ecosystems from the past and let them compete with the present day ecosystems. How would they compare? The ecosystem samples would have to be sufficiently large that species weren't penalized for co-evolutionary development. I.e., an insect feeds on a specific plant and a plant depends on a specific insect for pollination. Also they would need to be matched for similar environment parameters such as temperature and humidity. Could raptors compete with lions? Could ferns compete with grasses?

How would ancient bacteria compare with modern bacteria? Has there been significant bacterial advance in the past 600 million years?

Complexity may capture some aspects of evolutionary advancement. Human brain complexity has led to cultural evolution that is far more powerful than biological evolution. But what biological factors permitted increased complexity?

An interesting possibility is the efficiency of biological information processing. Efficiency might be measured by the metabolic cost for storing, transmitting, utilizing, adapting, and filtering information. Scientists could compare ancient and modern DNA/RNA/protein copying, repair, and regulatory systems and could compare ancient and modern nervous systems. Better information efficiency lowers the cost of increased complexity. Increased complexity in a complex, changing environment then permits better adaptive responses. (Clearly there are many environmental niches where simple is best. The microbal community is far more extensive than the multicellular community.)

Posted by: Fly | September 30, 2006 1:16 PM

Emerson,

"Oddly enough, the Dutch are at the top of the last list I saw (comparing nations, that is, and excluding the Dinka.)"

If you're implying the Dinka are on average taller than the Dutch, please backup this assertion. Hollywood movies and "Manute Bol is a Dinka" aren't evidence. Actual scientific evidence suggests the Dinka are not extraordinarily tall by European, much less Dutch, standards.

Posted by: professional mindfucker | October 1, 2006 3:28 PM

hey motherfucker, be respectful, john is a friend of mine. yes, the link you provided does suggest that the dinka aren't as tall as the perception, but, please note the title:
Anthropometric measurements of the Nilotic tribes in a refugee camp. do you know what a norm of reaction is? the northern european median height ain't half bad for a group that's been famined and genocided for the better part of 2 generations.

Posted by: razib | October 1, 2006 4:08 PM

Hey bitch, I don't care who your internet friends are. I give no respect to people who propagate myths. Sure, Dinka "could" possibly get taller given an ideal environment (a point made in the abstract I linked to). "Could maybe get tall" is not "are tall", and I'm aware of no anthropometric data from any period that gives a mean Dinka height appreciably higher than 5'9".

Posted by: professional mindfucker | October 1, 2006 4:35 PM

Just found this through a gnxp link. For what it's worth, the 1st edition of Evelyth and Tanner's book Worldwide Variation in Human Growth gives data on the height of Dinkas taken by Hiernaux (sp?) that I believe was done in the 1960s. I don't have the book in front of me right now, but I believe that the average height for Dinka's was 180.1 cm. This is pretty tall when you consider their living conditions compared to modern Europeans. However, if I'm not mistaken, the nilotic diet consists of lots of cow's milk and blood, so they may not be suffering from as much protein deficiency and stunting as one would at first think (perhaps much less than say traditional farming cultures from Eurasia whose diet mainly consisted of cereal products).
As for the average of 179cm for europeans 20k yrs ago, it may have arisen from genetic differences, but if they were largely big game hunters on an open tundra, they probably would have had a diet rich in protein and constant movement and low population densities would have meant that they also probably had a low level of environmental distress from infectious diseases that redarded the height of traditional agricultural societies.

Posted by: Hobbesian | March 19, 2007 2:46 AM