August 09, 2014
Natural Selection For Less Aggression Enabled Complex Societies

In order for human societies to grow in complexity and sophistication humans first had to evolve to become less aggressive. A greater capacity for cooperation was needed. Well, 50,000 years ago human skulls developed more rounded appearances with and brows became less heavy. Technology boom 50,000 years ago correlated with apparent reduction in testosterone

DURHAM, N.C. -- Modern humans appear in the fossil record about 200,000 years ago, but it was only about 50,000 years ago that making art and advanced tools became widespread.

A new study appearing Aug. 1 in the journal Current Anthropology finds that human skulls changed in ways that indicate a lowering of testosterone levels at around the same time that culture was blossoming.

I've been reading a lot of books lately on rises and declines of great civilizations. I've wondered whether a large scale settled society selects for less aggressive males which eventually makes it vulnerable to being overrun by a neighboring society that is less civilized. Take the Roman Empire for example. Were the Romans of 100 BC a more genetically masculine people than the Romans of 400 AD? Did their own success and long period of fairly safe living set them up to be overrun by genetically more masculine tribes sweeping down from northern Europe?

Cooperative temperaments are needed for larger scale human undertakings.

"The modern human behaviors of technological innovation, making art and rapid cultural exchange probably came at the same time that we developed a more cooperative temperament," said lead author Robert Cieri, a biology graduate student at the University of Utah who began this work as a senior at Duke University.

Lowering blood testosterone wasn't the only way this change could have come about. Testosterone binds on many receptors and activates many genetic regulatory systems. Lots of different places in the genome could have mutated to modify the effects of a given level of testosterone.

The study, which is based on measurements of more than 1,400 ancient and modern skulls, makes the argument that human society advanced when people started being nicer to each other, which entails having a little less testosterone in action.

Heavy brows were out, rounder heads were in, and those changes can be traced directly to testosterone levels acting on the skeleton, according to Duke anthropologist Steven Churchill, who supervised Cieri's work on a senior honors thesis that grew to become this 24-page journal article three years later.

Some features of the masculine mind (e.g. greater ability at spatial reasoning) would have remained advantages in some ecological niches. Especially before settled agriculture spatial reasoning would have enhanced hunting performance and therefore food supply.

After 150,000 years humans went thru a technological renaissance. The Upper Paleolithic was getting old and it was time to start preparing for the Middle Paleolithic. Sure, it was cold in the Ice Age. But intelligent manipulation of fire could make caves quite cozy.

There are a lot of theories about why, after 150,000 years of existence, humans suddenly leapt forward in technology. Around 50,000 years ago, there is widespread evidence of producing bone and antler tools, heat-treated and flaked flint, projectile weapons, grindstones, fishing and birding equipment and a command of fire. Was this driven by a brain mutation, cooked foods, the advent of language or just population density

What about selective effects for greater intelligence? Could the burst in tools making also come about due to selective pressures for higher intelligence? Maybe formation of tribes which internally had a greater willingness to cooperate created societies where being smart provided a bigger selective advantage. So the greater amount of cooperation created conditions for new selective pressures to emerge.

Another thing I wonder about: How much do variations in facial shapes across the world today represent sexual selective pressures for specific appearances, different selective pressures for masculinity or femininity, or just genetic drift? What are all the reasons why people come in so many shapes, sizes, and complexions?

And then there is my favorite question about human genetics: What happens to future humans when prospective parent start doing offspring genetic engineering? For example, do the girls become more feminine and the guys more masculine? Or do they converge? Do girls become taller? Or more in a narrower height band? What will be the most popular eye color or hair color? Will genetically engineered offspring be more or less cooperative? More or less motivated to work?

Share |      Randall Parker, 2014 August 09 09:37 PM 

James Bowery said at August 10, 2014 11:01 AM:

Watch this presentation by E. O. Wilson on his interpretation of human eusociality's contribution to human intelligence.

Then watch Suzana Herculano-Houzel's presentation on "What is so special about the human brain?".

Both claim that fire was the trigger but differ in how that played out during subsequent evolution.

E. O. Wilson believes that the camp fire created what he sees as the "protected nest" stage of incipient eusocial evolution and that once that barrier to eusociality had been overcome, social interactions drove the development of higher intelligence.

Suzana Herculano-Houzel believes that the camp fire provided the energy, in the form of cooked food's pre-digested chemistry, to support more neurons and that evolution has, for a very long time, been optimizing energy usage between body and brain being energy-constrained from evolving greater intelligence.

Its clear that primate evolution has included incipient eusocial capacities in the form of gang-warfare that is occasionally observed by chimps in the wild.

I tend to go with Suzana Herculano-Houzel for a very simple reason: Turing machine equivalence is generally applicable, whether one is talking about adapting to complex social environments or one is talking about adapting to complex natural environments. The complex social environment entailed by the evolution of eusociality will bias the intelligence toward understanding motives of others, but that only becomes important given the need to form gangs to fight other gangs. A bunch of girly-men in a gang can take down a lone he-man so, yes, one can say that civilization tends not to select for greater capacity for individual violence, but it is the height of stupidity to claim that by evolving away from greater individual violence the species as a whole is becoming less violent.

Look at the social insects where war first expressed in life forms -- the warriors are the dream come true of nonviolent cooperation where "Sisters are doin' it for themselves."

fb0252 said at August 10, 2014 7:02 PM:

ice age reduced game, forced euro humans closer to rivers and reliance on
eating fish instead of antelope. higher consumption of Omega 3, smarter
brains, presto, there u have it.

Ronald Brak said at August 10, 2014 11:39 PM:

Okay, just shootin' the breeze here, but if there was a technological revolution 50,000 years ago wouldn't weapons have improved and perhaps involved more stabbing, throwing, and shooting than smashing over the head? And as a result survival might not depended so much on having a thick skull but being agile enough to jump out of the way, or being fast enough to avoid or stab/pierce/shoot the person who wants to stab/pierce/shoot you first? After all, it only takes one punctured lung to really put a crimp in one's career as a hunter/gatherer.

Cluebat said at August 14, 2014 6:30 AM:

This article reeks of science activism.

Harold said at August 15, 2014 5:22 AM:

"What happens to future humans when prospective parent start doing offspring genetic engineering?"
I don't know, but if you choose the wrong traits according to your teenage daughter, it will be all your fault, and you will have ruined their entire life!
They don't care about being good at maths, they would rather be pretty!
Or maybe you can choose genes that make your children appreciative and happy with what they've got?
One thing I do know: those genes that predispose people to choose those same genes in turn for their children will survive, those that don't will perish.

Harold said at August 15, 2014 5:43 AM:

Here's a paper on testosterone and cooperation.

"February 2010, Eisenegger et al. reported increased fair bargaining behaviour after administration of testosterone in an ultimatum game1. However, unfair offers in the ultimatum game typically are rejected; thus, not only the motives for social cooperation but also the threat of financial punishment may have accounted for these effects. Here, using the public goods game (PGG), we unambiguously show increased social cooperation after testosterone administration, but only among subjects with low levels of prenatal testosterone."

More random thoughts on choosing genes:
Conservatives might choose genes which correlate with conservative beliefs and behaviours, liberals with liberal beliefs and behaviours.
Maybe we can give everyone alabaster skin, hair, and even eyes, and they can colour them, or decorate them, according to the current fashion.

Post a comment
Name (not anon or anonymous):
Email Address:
Remember info?

Go Read More Posts On FuturePundit
Site Traffic Info
The contents of this site are copyright