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Monday, March 14, 2011

Comparative Data Reveal Similar Mortality Patterns Across Primates and Humans

From the Montreal Gazette
Apes, like humans, 'age gracefully': study

Humans and wild primates share not only many physical features, they also experience similar aging patterns, according to a new collaborative study involving researchers from across North America.

The study, Aging in the Natural World, which appears in the March 11 issue of Science, reveals that humans and their hairier cousins see their risk of dying increase with age at similar rates.

"We know that humans have a higher risk of death in their infancy, which levels off for juveniles, picks up in adulthood and continues to increase with each year after that," said Dr. Linda Fedigan, co-author of the study and Canada research chair in primatology and bio-anthropology at the University of Calgary.

"We found a similar pattern in the non-human primates we studied."

It has always been assumed and widely accepted that humans age slower than most other mammals. But these conclusions were based on early research comparing human lifespans to those of shorter-lived species such as mice and rats, Fedigan said.

This new study is the first to compare human aging patterns with those of "our closest evolutionary relatives" involving the collaborative efforts of seven researchers undertaking long-term wild primate projects in different parts of the world.

Each researcher spent between 25 and 50 years observing different types of wild primates on a daily basis, noting when these animals were born, when they mated, gave birth, changed groups, got sick, and died.

Research data included findings from Jane Goodall's chimpanzee research site in Tanzania as well as Fedigan's own 28-year study on capuchin monkeys in Costa Rica.

Overall, the aging rates of 3,000 individual wild primates were measured.

When compared to findings from the U.S. Department of Health and Human Services on human aging, the research team determined that wild primates also "aged gracefully" and at a similar rate to humans.

The study also showed that wild male primates, like male humans, die sooner than their female counterparts.

Testosterone has long been believed to have a negative effect on the immune system, starting from within the womb, Fedigan said.

But the study suggests that male primates also face a higher risk of death compared to females due to the stress and aggression of male competition, which may be true for male humans.

Only one of the seven species — a Brazilian monkey called the muriqui — showed similar mortality patterns among males and females.

"It's a monkey species where males are known for being non-aggressive, non-competitive and are not fighting for access to females. In fact, they live in tight co-operative brotherhoods."

There are still many unanswered questions as to how long humans can live, especially with access to modern medicine and health care helping humans to live longer than before, Fedigan said.

"But with this study, we are one step closer to understanding factors that control, predict or affect the biological basis of the maximum human lifespan."

Bronikowski AM, Altmann J, Brockman DK, Cords M, Fedigan LM, Pusey A, Stoinski T, Morris WF, Strier KB, Alberst SC (2011) Aging in the Natural World: Comparative Data Reveal Similar Mortality Patterns Across Primates. Science 331 (6022): 1325-1328
DOI: 10.1126/science.1201571

Human senescence patterns—late onset of mortality increase, slow mortality acceleration, and exceptional longevity—are often described as unique in the animal world. Using an individual-based data set from longitudinal studies of wild populations of seven primate species, we show that contrary to assumptions of human uniqueness, human senescence falls within the primate continuum of aging; the tendency for males to have shorter life spans and higher age-specific mortality than females throughout much of adulthood is a common feature in many, but not all, primates; and the aging profiles of primate species do not reflect phylogenetic position. These findings suggest that mortality patterns in primates are shaped by local selective forces rather than phylogenetic history.

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