Brain size does not = intelligence in humans?

[Colin McHenry <cmchenry@westserv.net.au>]

Interesting article in view of the recent thread on dinosaur EQ ?

from:  http://www.abc.net.au/science/news/stories/s1702903.htm

posted below

Cheers
Colin

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Big head no sign of brilliant mind
Judy Skatssoon
ABC Science Online

  
Wednesday, 2 August 2006

Head
Genes that control head size are puzzling researchers who say they may 
also play a role outside the brain (Image: iStockphoto)
The genes that are thought to have helped humans evolve big brains don't 
appear to play any role in how intelligent we are, according to a DNA study.

This backs separate research that has failed to come up with a link 
between head size and intelligence, except in extreme congenital 
abnormalities.

The Queensland Institute of Medical Research (QMIR) study is the first 
to specifically look at genes, head size and intelligence in a normal 
population.

The Australian study found that people who scored highly in intelligence 
tests didn't necessarily possess versions of the genes that were 
expected to code for big heads and intelligence.

And people who did possess the suspected 'smart' versions of the genes 
weren't necessarily the most intelligent or the ones with the biggest 
brains.

The study will be presented at the 11th International Congress of Human 
Genetics in Brisbane next week.

Head space

The researchers tested 4395 teenagers for head size and intelligence.

They also looked at the genes ASPM, MCPH1 and CDK5RAP2, which regulate 
brain size and activity.

When mutated, these genes result in an abnormally small brain, a 
condition known as congenital microcephaly.

"Normal variation in these genes has not yet been investigated in 
relation to head
size and intelligence," says Dr Michelle Luciano, a research fellow at QMIR.

She says the only comparable previous study used MRI imaging to measure 
brain volume in relation to two microcephaly genes.

"Their findings [about a relation to brain size] were negative and they 
didn't find a relationship with two of the genes we were looking at," 
she says.

"We decided to take it a step further and look at intelligence and lo 
and behold we find a similar negative result."

Ancestral or evolved?

We all carry the three genes the QMIR team investigated but some of us 
carry 'ancestral', or less evolved, versions and others carry 'derived' 
or more recently evolved versions. Some of us carry one of each.

Researchers had expected that people with evolved versions of the gene 
would be smarter and have bigger heads, but were surprised to find this 
wasn't the case, Luciano says.

"We would predict that if you've got the more recent version you should 
have a higher IQ," she says.

"We actually found that not to be the case.

"It is unlikely then that selective pressure for these genes is related 
to the evolution of intelligence in humans."

Rather, she says the genes might be important for a neurological 
function outside the brain.

Are humans getting smarter?

Professor Colin Groves, an expert in human evolution from the Australian 
National University, says human brains began getting bigger after our 
earliest ancestors like Homo habilis appeared.

But our brains have stopped growing and have actually started getting 
smaller, or at least more 'compact'.

"[Our brains] have got bigger but they're not getting bigger," he says. 
"In fact since the late Pleistocene in general they've got smaller."

While brain size appears to be related to intelligence between species, 
this doesn't seem to be the case within a species, Groves says.

And despite the development of technological advances, he says there's 
no evidence that Homo sapiens has become more intelligent in the last 
50,000 years.


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Colin McHenry
School of Environmental and Life Sciences (Geology)
University of Newcastle
Callaghan NSW 2308
Australia
Tel: +61 2 4921 5404
Fax: + 61 2 4921 6925

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