Humans live longer than other mammals because we burn calories 50% slower
- Many mammals reach sexual maturity within a year - some within months
- A two-year-old dog, for example, can be between 18 and 25 in human years
- By comparison, primates reach adulthood later and reproduce less often
- Study claims this is because we burn half the calories of other mammals
- This means we put less energy into growing, which makes us age slower
- Humans would need to run a marathon every day to match energy released by similar-sized mammals
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The mystery as to why humans outlive almost all other mammals may have finally been solved.
An international team of scientists compared how much energy the average primate uses each day with the equivalent amount of energy other mammals use.
Researchers discovered, somewhat surprisingly, that primates burn half the calories of similar sized mammals, and that this slow metabolism slows down the ageing process.
An international team of scientists compared how much energy average primates, such as gorillas, pictured, use each day with the equivalent amount of energy other mammals use. Researchers discovered that primates burn half the calories of similar sized mammals
MAXIMUM LIFE SPANS OF MAMMALS
Animal Average life span (in years)
Mouse 4
Rat 7
Cats 14
Dogs 16
Polar bears 18
Horses 28
Elephants 70
Humans 82
The oldest living human, according to the Guinness Book of World Records, was a French woman called Jeanne Calmen who lived to 122.
To put this 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 study also found that primates in zoos expend as much energy as primates in the wild, suggesting physical activity may have less of an impact on the amount of calories they use than is often thought.
The majority of mammals, including rats and dogs, reach adulthood within a year or two. In fact, many mammals reach sexual maturity in a matter of weeks.
For example, a six-month-old rat is 18 in human years, while a two-year old dog is the equivalent of an 18- to 25-year-old human.
In the wild, these mammals also reproduce much more regularly than primates and many will die in their teens, if not before.
The majority of mammals, including dogs, left, and rats, right, reach adulthoods within a year or two. In fact, some mammals reach sexual maturity in a matter of weeks. For example, a six-month-old rat is 18 in human years, while a two-year old dog, is the equivalent of an 18- to 25-year-old human
By comparison, humans and our primate relatives, such as apes, monkeys, tarsiers, lorises, and lemurs, have long childhoods, reproduce infrequently, and live exceptionally long lives.
This slow pace of life has baffled biologists for some time because the mechanisms behind this difference were unknown.
Professor Herman Pontzer of Hunter College, New York, and colleagues, working with primates in zoos, sanctuaries, and in the wild examined the daily energy expenditure in 17 different primate species.
Using a safe and non-invasive technique known as ‘doubly labelled water,’ the researchers measured the number of calories that primates burned over a 10-day period.
Researchers examined the daily energy expenditure in 17 different primate species, including lemurs like the ones pictured. By combining these measurements with similar data from other studies, the team were able to compare this energy output to that of other mammals
Humans and their primate relatives live for longer because the slow rates of growth, reproduction, and ageing match their slow rate of energy expenditure
This technique tracks the body’s production of carbon dioxide, which gives an indication of how much energy they are expending.
By combining these measurements with similar data from other studies, the team were able to compare this energy output to that of other mammals.
This dramatic reduction in metabolic rate accounts for their slow pace of life.
All organisms need energy to grow and reproduce, and energy expenditure can also contribute to ageing.
The slow rates of growth, reproduction, and ageing among primates match their slow rate of energy expenditure, indicating that evolution has acted on metabolic rate to shape primates' distinctly slow lives.
‘The results were a real surprise,’ explained Professor Pontzer. ‘Humans, chimpanzees, baboons, and other primates expend only half the calories we'd expect for a mammal.
‘Understanding how human metabolism compares to our closest relatives will help us understand how our bodies evolved, and how to keep them healthy.’
While co-author Professor David Raichlen from the University of Arizona added: ‘The environmental conditions favouring reduced energy expenditures may hold a key to understanding why primates, including humans, evolved this slower pace of life.’
The findings have been published in the Proceeding of the National Academy of Sciences.
Read more: http://www.dailymail.co.uk/sciencetech/article-2539356/Mystery-mankinds-long-lifespan-solved-Humans-live-longer-mammals-burn-calories-50-slower.html#ixzz2qOr8SBi6