Evolution's twist
USC study finds meat-tolerant genes offset high cholesterol and
disease
When our human ancestors started eating meat, evolution served up a
healthy bonus – the development of genes that offset high cholesterol
and chronic diseases associated with a meat-rich diet, according to a
new USC study.
Those ancestors also started living longer than ever before – an
unexpected evolutionary twist.

The research by USC professors Caleb Finch and Craig Stanford appears
in Wednesday's Quarterly Review of Biology.

"At some point – probably about 2 1/2 million years ago – meat eating
became important to humans," said Stanford, chair of the anthropology
department in the USC College of Letters, Arts and Sciences, "and when
that happened, everything changed."

"Meat contains cholesterol and fat, not to mention potential parasites
and diseases like Mad Cow," he said. "We believe humans evolved to
resist these kinds of things. Mad Cow disease – which probably goes
back millions of years – would have wiped out the species if we hadn't
developed meat-tolerant genes."

Finch, the paper's lead author, and Stanford found unexpected treasure
troves in research ranging from chronic disease in great apes to the
evolution of the human diet. They also focused on several genes,
including apolipoprotein E (apoE), which decreases the risk of
Alzheimer's and vascular disease in aging human adults.

Chimpanzees – who eat more meat than any other great ape, but are
still largely vegetarian – served as an ideal comparison because they
carry a different variation of the apoE gene, yet lack human
ancestors' resistance to diseases associated with a meat-rich diet.

While chimpanzees have a shorter life span compared to humans, they
demonstrate accelerated physical and cerebral development, remain
fertile into old age and experience few brain-aging changes relative
to the devastation of Alzheimer's seen in humans today. Finch and
Stanford argued that the new human apoE variants protected the
chimpanzees.

In a series of "evolutionary tradeoffs," the researchers said, humans
lost some advantages over those primates, but gained a higher
tolerance to meat, slower aging and longer lifespan.

Still, if humans developed genes to compensate for a meat-rich diet,
why do so many now suffer from high cholesterol and vascular disease?

The answer is a lack of exercise and moderation, according to the
researchers.

"This shift to a diet rich in meat and fat occurred at a time when the
population was dominated by hunters and gatherers," said Finch, a USC
University Professor and holder of the ARCO-William F. Kieschnick
Chair in the Neurobiology of Aging.

"The level of physical activity among these human ancestors was much
higher than most of us have ever known," he said. "Whether humans
today, with our sedentary lifestyle, remain highly tolerant to meat
eating remains an open question researchers are looking into."

Stanford, co-director of the university's Goodall Research Center,
said that modern-day humans "tend to gorge ourselves with meat and
fat."

"For example, our ancestors only ate bird eggs in the spring when they
were available," he said. "Now we eat them year-round. They may have
hunted one deer a season and eaten it over several months. We can go
to the supermarket and buy as much meat as we want."

"I think we can learn a lesson from this," Stanford said. "Eating meat
is fine, but in moderation and with a lot of exercise."

http://www.eurekalert.org/pub_releas...c-et031904.php