Multiple causes for human brain evolution; social competition most important

[Oolon Colluphid]

Human Nature Vol. 20 Issue 1, p67-79 (March 2009)

Hominid Brain Evolution

Bailey and Geary

Hypotheses regarding the selective pressures driving the threefold increase in the size of the hominid brain since Homo habilis include climatic conditions, ecological demands, and social competition.

We provide a multivariate analysis that enables the simultaneous assessment of variables representing each of these potential selective forces.

Data were collated for latitude, prevalence of harmful parasites, mean annual temperature, and variation in annual temperature for the location of 175 hominid crania dating from 1.9 million to 10 thousand years ago.

We also included a proxy for population density and two indexes of paleoclimatic variability for the time at which each cranium was discovered.

Results revealed independent contributions of population density, variation in paleoclimate, and temperature variation to the prediction of change in hominid cranial capacity (CC).

Although the effects of paleoclimatic variability and temperature variation provide support for climatic hypotheses, the proxy for population density predicted more unique variance in CC than all other variables.

The pattern suggests multiple pressures drove hominid brain evolution and that the core selective force was social competition.

Thread on this.

Tags: human brain hominid capacity competition

[Oolon Colluphid]

Annoyingly, I get a "Most recent 6 months not available" from the OU library, so all we've got is the abstract.

But this result fits quite well with hypotheses about the reason for our big brains being outsmarting other people, rather than just being generally clever for other reasons. A standard maxim in ecology is that, predators, prey etc be damned: there's no tougher competition than with members of your own species.

[Cath B]

This seems to tie in with stuff I've come across here and there (Robin Dunbar, Geoffrey Miller maybe?).

An important environmental pressure that could be handled more effectively by having a versatile, intelligent brain was lots of other folk with versatile, intelligent brains.

Social cooperation can be a form of social competition IMO.

Folk with an ability to charm, cooperate, woo folk as friends and mates could score well.

And if such Machiavellianism is unconscious (i.e. he/she really enjoys being kind, considerate etc.) so much the better.

[DMB]

If you look at chimp society as a model, they have smaller social groupings than human natural groups. But within their groups, they not only have to understand status, they also have to remember who has done them good and bad turns. As groups get bigger, this must require a lot more processing power.

[David B]

If you look at chimp society as a model, they have smaller social groupings than human natural groups. But within their groups, they not only have to understand status, they also have to remember who has done them good and bad turns. As groups get bigger, this must require a lot more processing power.

Some people have attributed group size to the development of language - a less time consuming method of grooming, and one that can be used on more than one group member at a time.

David

[Worldtraveller]

Annoyingly, I get a "Most recent 6 months not available" from the OU library, so all we've got is the abstract.

But this result fits quite well with hypotheses about the reason for our big brains being outsmarting other people, rather than just being generally clever for other reasons. A standard maxim in ecology is that, predators, prey etc be damned: there's no tougher competition than with members of your own species.
I'd say competition amongst different species that predate on the same prey (lions and hyenas) might be a close ....errr... competion. :p

[VoxRat]

This seems to tie in with stuff I've come across here and there (Robin Dunbar, Geoffrey Miller maybe?).

An important environmental pressure that could be handled more effectively by having a versatile, intelligent brain was lots of other folk with versatile, intelligent brains.

Social cooperation can be a form of social competition IMO.

Folk with an ability to charm, cooperate, woo folk as friends and mates could score well.

And if such Machiavellianism is unconscious (i.e. he/she really enjoys being kind, considerate etc.) so much the better.
I don't know who Dunbar is, but I've read Miller's book (http://www.amazon.com/exec/obidos/ASIN/0385495161/ref%3Dnosim/thefriedrhayeksc/104-9304036-6565515#reader), which casts human brain development as an example of sexual selection.

Here's where the terminology gets dicey for me. Is there a clear distinction between "social competition" and "sexual selection"?