Comments on: The evolution of human intelligence

By: Stefan Krueger

Stefan Krueger — Sun, 05 Jul 2009 19:41:42 +0000

The throwing objects hypothesis isn’t too strong. Most of the really complex calculations done for sensorymotor tasks occur in the Cerebellum. Compared to other species, it actually takes up a much smaller percentage of brain matter. It is in the neocortex where human brains are substantially larger, and it is here where social interaction is processed.

By: Joshua Zelinsky

Joshua Zelinsky — Wed, 24 Jun 2009 22:01:33 +0000

Ah, that’s why he sounded familiar.

By: razib

razib — Tue, 23 Jun 2009 22:01:43 +0000

joshua, calvin has promoted the throwing ideal.

By: Joshua Zelinsky

Joshua Zelinsky — Tue, 23 Jun 2009 20:00:46 +0000

Given that cranial capacity and brain size isn’t a perfect correlation (the recent Sibyrhynchus fossil comes to mind for example) and given that brain size isn’t always correlated with intelligence this seems questionable.
Since only one extant species seems to have evolved to the high levels of intelligence that humans have, it really is very hard to do much more than speculate about what caused human intelligence.
One hypothesis that I like a little bit (and unfortunately forget who proposed it) is that large brains developed specifically for the ability to throw objects effectively. From a math perspective, this is a good idea because the calculations that humans do when they throw or catch irregular objects are really quite complicated.
Also, an interesting note: Some birds and apes have larger counting numbers than most humans. There was a study recently showing that the average chimp counting number was around 8.

By: ben g

ben g — Tue, 23 Jun 2009 18:06:26 +0000

cranial capacity and intelligence – i think this is a weak proxy for intelligence. between species, yeah, you have differences that correlate w/ intelligence, but you also have species with much larger brains than us. within our species, the cranial capacity -> intelligence idea is fraught with problems as well. i don’t think that it’s possible to start making reliable evolutionary conjectures with any of this. eventually we’ll have a neuroscientific understanding of intelligence, and maybe we can look precisely at that to see how its evolved.
population density and intelligence – so, they’re correlated. what is the evidence that the former is causing the latter?
encephalization and intelligence – also correlated, but i’m yet to see evidence for a causal arrow. a multivariate genetic analysis could possibly answer whether the two share genes, but i think we’d still be at the point where we’re unable to produce reliable evolutionary theories from it.

By: John Hawks

John Hawks — Tue, 23 Jun 2009 16:20:03 +0000

Your BS detector should be set higher. How exactly did they estimate “population density” for the past 2 million years?
We assume a close relationship between population density and migration patterns—
this is apparent in the fossil record (see Results)—and thus created a population
density proxy using the number of individuals living in surrounding areas during the
hominid’s ancestral history. The population density score for cranium j is represented
as the number of crania dated from the same date or before j, outside a radius of 30°
(in any direction) of Al Mashriq, Ethiopia.
In other words, the spatial extent of humanity is their measure of “population density.” Of course, spatial extent is autocorrelated with time. As is cranial capacity. QED
D’oh!
All their analysis is showing is that climate doesn’t explain human colonization.