[ExI] Human brains better tooled up than monkeys

Dave Sill sparge at gmail.com
Wed Sep 16 17:44:36 UTC 2009


Human brains light up when they see tools being used – but the sight
fails to impress the brains of macaque monkey, our fellow primates, in
the same way.

In people, a particular brain region responds to tool use. This could
have enabled early humans to understand how and why a tool worked,
because it gave them early insights into cause and effect. Armed with
this knowledge, they could work out in advance how tools could be used
or modified to solve a multitude of new problems.

Monkeys, by contrast, can be taught to use a tool to obtain a reward,
but have little or no insight into the underlying concepts and forces
that make it work.

"It meant humans could understand things much more rapidly," says Guy
Orban of the Catholic University of Leuven in Belgium, the head of the
team that discovered the uniquely human area.

"To get an associative understanding between tool and reward, monkeys
must do things many times to learn by trial and error," he says. "But
once understanding was genetically programmed to be there, humans
could begin solving each new problem from a much higher level."

Home improvement channel

Orban and his colleagues identified the unique area, called the
anterior supramarginal gyrus (aSMG), through experiments in which
people and monkeys watched videos of simple tools being used while
their brains were scanned with fMRI.

Forty-seven people and five rhesus monkeys participated in the
experiments. Two of the monkeys had been trained to obtain rewards
beyond their reach by using either a rake or a pair of pliers.

Exactly the same areas of the brain became active in people and
monkeys when they watched footage of hands simply grasping tools.

But when they watched videos of tools actually being used, the aSMG
became active in the humans alone. It was silent even in the two
trained monkeys'.

Tool Age

Orban and his colleagues think that the region may be specific to
understanding cause and effect in tools alone: other brain regions
have been seen to be active in more general studies of "cause and

"This is only the first step towards use of tools," says Orban.
Further brain changes were probably necessary in the prefrontal cortex
– the thinking and reasoning part of the brain – before our ancestors
could envisage and plan complex tools that would embody subsidiary
goals as well as a main objective.

Orban says that the earliest evidence for human-like tool use dates
back 2.5 million years ago, to sharp-edged flakes from the so-called
Oldowan culture of the Lower Palaeolithic period in Africa.

The aSMG was also seen to be active during earlier experiments in
which contemporary people fashioned tools like those from the Oldowan
period while having their brains scanned.

Unfair advantage

"This region is implicated in understanding the action possibilities
that a tool affords, which could be a critical component in the kind
of flexible and creative tool use characteristic of humans," says
Dietrich Stout of Emory University in Atlanta, Georgia, who carried
out the toolmaking experiments .

"This is very exciting because we are closing in on unique aspects of
human tool use," he says.

But one caveat, says Stout, is that the monkeys only had a month of
training on each task, whereas the people in his experiments were
archaeologists with at least 10 years' experience of making Oldowan
tools. So the monkeys may not have had sufficient time to develop the
necessary brain architecture.

Further work will be needed to reveal whether the aSMG region is
active in chimpanzees and other apes much more adept than monkeys at
using tools.

Nor does the new research explain the extraordinary abilities of other
creatures, particularly birds, to deploy tools, sometimes from first

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