[PEN-L:28058] RE: economic imperialism and brain evolution

["Devine, James" <jdevine@xxxxxxx>]

Title: RE: [PEN-L:28056] economic imperialism and brain evolution

for a good book on the origins of humanity that avoids reductionism and economistic ideas, see David Horrobin, THE MADNESS OF ADAM & EVE: HOW SCHIZOPHRENIA SHAPED HUMANITY (London: Bantam, 2001). Refusing to accept the idea that enviromental factors alone encouraged big brains, etc., Horrobin talks a lot about possible mutations that helped, getting into issues of fatty acids in the brain, schizophrenia, etc.

JD

-----Original Message-----
From: Ian Murray
To: pen-l
Sent: 7/15/2002 5:53 PM
Subject: [PEN-L:28056] economic imperialism and brain evolution

Human brain "paid off" by long life
22:00 15 July 02
NewScientist.com news service

A theory portraying children as start-up companies and
middle-aged adults as their investors has been proposed to
explain why humans have such big brains and long life spans.

Evolutionary biologists have puzzled for decades over why
humans live twice as long as chimpanzees and gorillas and have
brains three to four times larger than their closest living
relatives.

"We're thinking of the brain as an investment," says economist
Arthur Robson, at the University of Western Ontario. Robson
and anthropologist Hillard Kaplan, at the University of New
Mexico, believe this investment is so substantial that it
requires a longer human life span to give it the time to pay
off.

"The combination of issues that they raise is novel - a useful
first step," says evolutionary biologist Michael Rose, at the
University of California at Irvine. But he warns against
putting too much confidence in a mathematical model: "If
you're a good applied mathematician, you can come up with a
model to give you any conclusion you want."

Nonetheless, Rose is intrigued by the explanation of why human
children are so unproductive for so long. "This is the best
paper on the evolution of teenagers I've ever read," he says.

Enormous debt

The inspiration for Robson and Kaplan's theory came from the
observation that children in modern day hunter-gatherer
societies consume more calories than they produce,
accumulating an enormous debt that peaks at age 20.

As active young adults, they produce more than they consume,
but it takes decades to pay off their childhood debt. Only at
age 50 do they start moving out of the red and into the black.
They then begin to make a net contribution of resources to
their society, offsetting the debt of the children in the next
generation.

The researchers noticed the parallels between the energy flows
in these societies and cash flows in start-up companies, and
applied an economic model to human evolution. They treated
physical and mental capacities as "embodied capital", with the
brain representing a special form of capital that increases in
value over time.

Predator protection

According to the model, the brain requires such an enormous
investment of energy during childhood that human ancestors
must have evolved long life spans to make that initial
investment worthwhile.

Robson and Kaplan believe these early humans must have lived
in an environment where food gathering was complicated,
favouring the development of big brains. They also suspect
that the environment reduced the risk of premature death by
affording some protection from predators.

The model therefore assumes that the environment was the key
factor shaping human evolution. But, Rose argues, this leaves
out the sophisticated social interactions that must have also
contributed to development.

Journal reference: Proceedings of the National Academy of
Sciences (DOI: 10.1073/pnas.152502899)

Robin Orwant