we are evolving to eat mush

More the the great meat eating debate.
My take: We eat both. Neither meat or veggies are
more natural.



"Evolving to Eat Mush": How Meat Changed Our Bodies
Hillary Mayell
for National Geographic News
February 18, 2005

Meat-eating has impacted the evolution of the human body,
scientists reported today at the American Association for the
Advancement of Science's annual meeting in Washington, D.C.

Our fondness for a juicy steak triggered a number of adaptations
over countless generations. For instance, our jaws have gotten
smaller, and we have an improved ability to process cholesterol
and fat.

Our taste for meat has also led us into some trouble—our teeth
are too big for our downsized jaws and most of us need dental
work.

"It's really amazing what we know now that we didn't know 15 or
20 years ago," said Mark Teaford, a professor at Baltimore's
Johns Hopkins University. Teaford helped organize a panel
discussion on human diet from a number of perspectives:

• How did the ability to eat meat shape the evolution of humans?
• What can we learn about early humans from tooth shape?

Carnivorous humans go back a long way. Stone tools for
butchering meat, and animal bones with corresponding cut marks
on them, first appear in the fossil record about 2.5 million
years ago.

How Did Meat-Eating Start?

Some early humans may have started eating meat as a way to
survive within their own ecological niche.

Competition from other species may be a key element of natural
selection that has molded anatomy and behavior, according to
Craig B. Stanford, an ecologist at the University of Southern
California (USC).

Stanford has spent years visiting the Bwindi Impenetrable Forest
National Park in Uganda, Africa, studying the relationship
between mountain gorillas and chimpanzees.

"It's the only forest where mountain gorillas and chimps both
live," he said. "We're trying to understand the ecological
relationship—do they compete for food, for nesting sites?"

The key difference between chimps and gorillas ecologically is
that chimps eat meat and gorillas don't. A total herbivore is
able to coexist with an omnivore because they have significantly
different diets.

"From there we can extrapolate back to what two species of early
humans may have done vis-à-vis each other two or three million
years ago," Stanford said.

Better Fat Processors

When humans switched to meat-eating, they triggered a genetic
change that enabled better processing of fats, said Stanford,
who has worked extensively with gerontologist Caleb Finch of
USC.

"We have an obsession today with fat and cholesterol because we
can go to the market and stuff ourselves with it," Stanford
said. "But as a species we are relatively immune to the harmful
effects of fat and cholesterol. Compared to the great apes, we
can handle a diet that's high in fat and cholesterol, and the
great apes cannot.

"Even though we have all these problems in terms of heart
disease as we get older, if you give a gorilla a diet that a
meat-loving man might eat in Western society, that gorilla will
die when it's in its twenties; a normal life span might be 50.
They just can't handle that kind of diet."

Diet and Teeth

Tool-use no doubt helped early humans in butchering their
dinners. But there is evidence that the advance to cooking and
using knives and forks is leading to crooked teeth and facial
dwarfing in humans.

Today it's relatively rare for someone to have perfectly
straight teeth (without having been to the orthodontist). Our
wisdom teeth don't have room to fit in the jaw and sometimes
don't form at all, and the propensity to develop gum disease is
on the increase.

"Virtually any mammalian jaw in the wild that you look at will
be a perfect occlusion—a very nice Hollywood-style dentition,"
said Peter Lucas, the author of Dental Functional Morphology and
a visiting professor at George Washington University in
Washington, D.C. "But when it comes to humans, the ideal
occlusion [the way teeth fit together] is virtually never seen.
It's really the only body part that regularly needs attention
and surgery."

Lucas argues that the mechanical process of chewing, combined
with the physical properties of foods in the diet, will drive
tooth, jaw, and body size, particularly in human evolution.

Essentially, by cooking our food, thereby making it softer, we
no longer need teeth big enough to chow down on really tough
particles. By using knives and forks to cut food into smaller
pieces, we no longer need a large enough jaw to cram in big
hunks of food.

"We're evolving to eat mush," said Bernard Wood, a
paleoanthropologist at George Washington University.

http://news.nationalgeographic.com/n...uman_diet.html

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