Sara S
12-12-2008, 09:40 AM
In today's encore excerpt--raw versus cooked.
Since brain
tissue requires 22 times the food energy that skeletal
muscle does, Homo erectus would have had to chew
raw food for six hours each day to obtain enough food
energy to sustain its brain size. This fact has led to
Harvard anthropologist Richard Wrangham's
controversial theory that fire and cooking were the
necessary steps that allowed for the evolution of
larger brains:
" 'I tend to think about human evolution through the
lens of chimps,' Wrangham remarks. 'What would it
take to convert a chimpanzee-like ancestor into a
human?' Fire to cook food, he reasoned, which led to
bigger bodies and brains. And that is exactly what he
found in Homo erectus, our ancestor that first
appeared 1.6 million to 1.9 million years ago. H.
erectus's brain was 50 percent larger than that of its
predecessor, H. habilis, and it experienced the
biggest drop in tooth size in human evolution. 'There's
no other time that satisfies the expectations that we
would have for changes in the body that would be
accompanied by cooking,' Wrangham says.
"The problem with his idea: proof is slim that any
human could control fire that far back. Other
researchers believe cooking did not occur until
perhaps only 500,000 years ago. ...
"So Wrangham did more research. He examined
groups of modern hunter-gatherers all over the world
and found that no human group currently eats all their
food raw. Humans seem to be well adapted to eating
cooked food: modern humans need a lot of high-
quality calories (brain tissue requires 22 times the
energy of skeletal muscle); tough, fibrous fruits and
tubers cannot provide enough. Wrangham and his
colleagues calculated that H. erectus (which was in H.
sapiens's size range) would have to eat roughly 12
pounds of raw plant food a day, or six pounds of raw
plants plus raw meat, to get enough calories to
survive. Studies on modern women show that those
on a raw vegetarian diet often miss their menstrual
periods because of lack of energy. Adding high-energy
raw meat does not help much, either--Wrangham
found data showing that even at chimps' chewing rate,
which can deliver them 400 food calories per hour, H.
erectus would have needed to chew raw meat for 5.7
to 6.2 hours a day to fulfill its daily energy needs.
When it was not gathering food, it would literally be
chewing that food for the rest of the day. ... [Animals]
expend less effort breaking down cooked food than
raw. Heat alters the physical structure of proteins and
starches, thereby making enzymatic breakdown
easier.
"Wrangham's theory would fit together nicely if not for
that pesky problem of controlled fire. Wrangham
points to some data of early fires that may indicate that
H. erectus did indeed tame fire."
Rachael Moeller Gorman, "Cooking Up Bigger
Brains," Scientific American, January 2008, pp.
102-104.
From: delancyplace.com
----------------------------------------
Since brain
tissue requires 22 times the food energy that skeletal
muscle does, Homo erectus would have had to chew
raw food for six hours each day to obtain enough food
energy to sustain its brain size. This fact has led to
Harvard anthropologist Richard Wrangham's
controversial theory that fire and cooking were the
necessary steps that allowed for the evolution of
larger brains:
" 'I tend to think about human evolution through the
lens of chimps,' Wrangham remarks. 'What would it
take to convert a chimpanzee-like ancestor into a
human?' Fire to cook food, he reasoned, which led to
bigger bodies and brains. And that is exactly what he
found in Homo erectus, our ancestor that first
appeared 1.6 million to 1.9 million years ago. H.
erectus's brain was 50 percent larger than that of its
predecessor, H. habilis, and it experienced the
biggest drop in tooth size in human evolution. 'There's
no other time that satisfies the expectations that we
would have for changes in the body that would be
accompanied by cooking,' Wrangham says.
"The problem with his idea: proof is slim that any
human could control fire that far back. Other
researchers believe cooking did not occur until
perhaps only 500,000 years ago. ...
"So Wrangham did more research. He examined
groups of modern hunter-gatherers all over the world
and found that no human group currently eats all their
food raw. Humans seem to be well adapted to eating
cooked food: modern humans need a lot of high-
quality calories (brain tissue requires 22 times the
energy of skeletal muscle); tough, fibrous fruits and
tubers cannot provide enough. Wrangham and his
colleagues calculated that H. erectus (which was in H.
sapiens's size range) would have to eat roughly 12
pounds of raw plant food a day, or six pounds of raw
plants plus raw meat, to get enough calories to
survive. Studies on modern women show that those
on a raw vegetarian diet often miss their menstrual
periods because of lack of energy. Adding high-energy
raw meat does not help much, either--Wrangham
found data showing that even at chimps' chewing rate,
which can deliver them 400 food calories per hour, H.
erectus would have needed to chew raw meat for 5.7
to 6.2 hours a day to fulfill its daily energy needs.
When it was not gathering food, it would literally be
chewing that food for the rest of the day. ... [Animals]
expend less effort breaking down cooked food than
raw. Heat alters the physical structure of proteins and
starches, thereby making enzymatic breakdown
easier.
"Wrangham's theory would fit together nicely if not for
that pesky problem of controlled fire. Wrangham
points to some data of early fires that may indicate that
H. erectus did indeed tame fire."
Rachael Moeller Gorman, "Cooking Up Bigger
Brains," Scientific American, January 2008, pp.
102-104.
From: delancyplace.com
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