Humans and other primates burn 50 percent fewer calories daily than other
mammals, U.S. scientists say, explaining why we grow so slowly and live long
Researchers at Chicago's Lincoln Park Zoo were part of a team of researchers in
a study that examined the proposition primates' slow pace of life results from a
slow metabolism, the zoo reported Wednesday.
Most mammals live a fast-paced life, reaching adulthood in a matter of months,
reproducing prodigiously and dying in their teens if not well before.
In comparison, humans and our primate relatives have long childhoods, reproduce
infrequently and live exceptionally long lives.
Working with primates in zoos, sanctuaries, and in the wild, the researchers
used safe and non-invasive methods to measure the number of calories that
primates burned in a 10-day period.
"The results were a real surprise," Herman Pontzer, an anthropologist at Hunter
College in New York and the lead author of the study, said in a Lincoln Zoo
release. "Humans, chimpanzees, baboons, and other primates expend only half the
calories we'd expect for a mammal.
"To put that in perspective, a human -- even someone with a very physically
active lifestyle -- would need to run a marathon each day just to approach the
average daily energy expenditure of a mammal their size."
The slow rates of growth, reproduction and aging among primates match their slow
rate of energy expenditure, indicating evolution has acted on metabolic rate to
shape primates' distinctly slow lives, the researchers said.
"The environmental conditions favoring reduced energy expenditures may hold a
key to understanding why primates, including humans, evolved this slower pace of
life," said study co-author David Raichlen, an anthropologist at the University
Linking growth, reproduction and aging to daily energy expenditure may shed
light on the processes by which our bodies develop and age, the researchers
said, and could improve our understanding of obesity and other metabolic