Image: Baboons
Science / AAAS
Adult female baboons sit with an infant being groomed in Amboseli, Kenya. Researchers have found that baboons and other primates age much as humans do, with a relatively high risk of dying in infancy, a low risk during the juvenile years and then an increased risk as aging progresses.
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updated 3/10/2011 2:52:57 PM ET 2011-03-10T19:52:57

The patten of aging in humans is not too different from most other primates, such as chimpanzees, monkeys and baboons, new research shows.

A team led by Anne Bronikowski of Iowa State University studied data on primate aging collected over decades around the world and compared it with statistics on modern Americans. Aging was defined as the increased risk of dying from natural causes while getting older. Some experts have thought that because people have relatively long life spans, humans aged differently from other mammals.

The research team believed that any major difference between humans and primates was most likely to show up with modern people, rather than a hunter-gatherer culture, Bronikowski said in a telephone interview. "And the fact that we don't find a difference there is more compelling."

The basic pattern they found is a relatively high risk of dying in infancy, a low risk of death during the juvenile years and then an increased risk of dying as aging progressed. Also, they found that in most cases males don't live as long as females.

"Human patterns are not strikingly different, even though wild primates experience sources of mortality from which humans may be protected," the authors wrote in a study published online Thursday in the journal Science.

The lone exception to the general pattern was the muriqui monkey in Brazil; males and females have similar life spans. Unlike other primates, muriqui males do not compete with each other for access to females. Instead, they cooperate with each other, explained co-author Karen Strier, an anthropologist at the University of Wisconsin who has studied muriquis since 1982.

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The researchers said the reason males of other species die earlier than females may be a result of the stress of competition.

Joseph W. Kemnitz of the Wisconsin National Primate Research Center called the study "an important step" because it provides the first assessment of patterns of aging in large populations of nonhuman primates living in their natural environments. Kemnitz was not part of the research team.

The "hard-won data will be welcomed by all of us interested in comparing patterns of actuarial aging both among species and among populations of the same species," added anthropology professor Kristen Hawkes of the University of Utah.

"The study of other primates contributes to understanding human aging because we share so much of our basic physiology," added Hawkes, who was not part of the research team.

© 2012 LiveScience.com. All rights reserved.

Explainer: Good times of the animal kind

  • Getty Images

    Who knows what's causing this cohort of cubicle warriors to buckle over in laughter, but few humans would disagree that a good chuckle every now and again feels good. Monkeys, dogs and fish get a kick out of life as well, says Jonathan Balcombe, a senior research scientist with the Physicians Committee for Responsible Medicine in Washington, D.C. He has written several research papers and books on animal pleasure, including "Exultant Ark: A Pictorial Tour of Animal Pleasures," due out next year. Click the "Next" arrow above for an overview of good times in the animal kingdom.

  • Man's best friend is full of expression

    David Bolton  /  Morguegfile,com

    Dogs, a slate of research suggests, are full of expression. "Those who live with dogs know that by looking at the body posture and the tail movements and the facial expressions and the sounds they make, we can sort of divine how they are feeling; whether they are feeling up or down, excited or grim or guilty, or what have you," Balcombe says. Even people who haven't lived with dogs, studies show, are able to read dog behavior, he adds. "We can only imagine how well dogs can read dogs, but dogs 'dogamorphize,' I suppose, and being dogs — with their keen sense of smell, for example — they get a lot more information than we do."

  • Horses' heart rates drop when groomed

    Reed Saxon  /  AP

    Look to horses for biological evidence that animals can feel pleasure. Balcombe notes that studies have found, for example, that horses' heart rates drop when they are groomed on parts of their necks and withers. A drop in heart rate "is known to be a response to feeling good and feeling relaxed," he says. In this image, Mike Polder comforts his horse Rowdy who was recovering from a West Nile virus infection.

  • Rats like to be tickled

    Brandi Saxton

    When young rats — the rodents that some humans love to hate — are seen running around wrestling with each other, they are actually in what equates to a tickle fight, according to research led by Jaak Panskeep at Washington State University. The rats, it appears, love to be tickled. His work, cited by Balcombe, shows that rats that have been trained to expect a belly tickle will approach a researcher's hand much more quickly than a rat that knows it'll just receive a neck rub.

  • Monkey massages are calming

    Arthur Sevestre

    Observations indicate that monkeys like to cuddle, such as those shown here, and give massages. Balcombe says these rub downs cause monkey blood chemistry and hormone levels to change in ways "that are consistent with what we would find in ourselves when we are receiving a massage." The biochemical finding, he adds, is another window into how animals experience pleasure.

  • Sexual activity not always for procreation

    Mitch Reardon  /  Lonely Planet Images

    As many humans know, sexual activity isn't always for the purpose of making a baby. The animal kingdom is full of examples of creatures that get it on just 'cause, says Balcombe. Among giraffes, for instance, homosexual activity is often more common than heterosexual activity. And even when the act is in the direction of procreation, Balcombe says that most animals probably don't connect the dots between their pleasure seeking and babymaking.

  • Fish go in for a cleaning

    Gerry Allen / The Swedish Research Council

    Balcombe's studies on animal pleasure are, in part, a pushback against the scientific community's penchant for parsing animal behavior in strict evolutionary terms. For example, the relationship between cleaner fish and their clients is often described as one of mutual benefit. The cleaners get food from the parasites on the clients' bodies and the clients get cleaned. "But I think the reason the fish go there is because it feels good. I don't think the fish clients are aware of any health benefit," he says. "So I do think that's a pleasure driven interaction."

  • Squirrels chase each other for fun

    Arthur Sevestre

    The squirrels shown here chasing each other around a tree are just playing around, according to Balcombe. While play behavior may have evolutionary underpinnings such as learning to escape from predators and tackle prey, Balcombe argues in a recent review paper in the journal Applied Animal Behavior Science that animals "do not consciously play for ultimate reasons: they play because it is fun to do so."

  • Dolphin looks can be deceiving

    Chris Gotshall  /  Reuters file

    Is this bottlenose dolphin happy to be bonding with her newborn calf? Despite a vast scientific literature on dolphin intelligence and scant doubt that they can feel pleasure, Balcombe says little can be gleaned from their facial expressions. Dolphins, he notes, have fairly fixed expressions. "The important thing with interpreting other animal's feelings is to know the animal, to know their biology, to know how they work," he says.

  • A calf runs free

    Connie Pugh

    Whitaker, a calf freed from a factory farm operation, enjoys a good run in this image. Balcombe, who has been a vegetarian for 25 years, says he grew up eating meat and "grew to love it." He stopped his carnivore ways out of concerns for animal welfare and thinks the growing body of research on animal feelings along with research showing adverse effects on the planet's health from animal agriculture will motivate other people to change their diets too.

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