Science of love
A group of baboons travels through their
home range in the Amboseli basin, at the foot of snow-capped Mt
Kilimanjaro near the equator in East Africa. (click
photo for larger view)
Photo by Joan Silk
One female baboon grooms another. The result
is not just fewer ticks, but stronger social bonds, and better infant
survival. Photo by Beth Archie
| Former kids, fess
up: Didn't you feel ignored while mom spent those hours blabbing with
her girlfriends? Between phone time and face time, mom had hardly
a moment to lavish attention on poor 'ol you. How truly tragic!
But it turns out that you may have crummy cause
for complaint. It could be that mom's ardently maintained social
connections helped you reach the age of reason, or at least, the
age of complaint.
That's a leap, but a logical leap, that one might make from a new study showing that infant baboons had a higher chance of surviving their first year of life if mom hung tight with the homeys, as measured by the amount of time spent grooming and simply hanging out.
The research elaborates on a rich body of evidence showing that social ties improve health, mood and quality of life among Homo sapiens.
In evolutionary terms, it indicates that social bonds offer a survival advantage. In other words, if mom's connected to a social network, more of her genes will appear in future generations, which meets the definition of Darwinian fitness. And to the extent that mom's shmoozability is coded in the genes of offspring, they would have a reinforced urge to connect if they have the genes for sociability.
This is good news for the phone company, especially
the cell-phone companies that sell to non-human primates in Amboseli
National Park, Kenya, where the baboons in question live. But before
we spill all the results, it wouldn't hurt to find out what the
researchers actually did.
Silk, a professor of anthropology at the University of California
at Los Angeles, Jeanne Altman, in the department of ecology and
evolutionary biology at Princeton University, and Susan Alberts,
in the department of biology at Duke University, examined data on
baboons living in Amboseli. Here, in the shadow of Mt. Kilimanjaro, baboons live in groups of roughly 60 to 80
The data, from 34,000 observations of 108 females,
were assembled by the Amboseli Baboon Research Project, which has
data dating back to 1971. "The goal all along was to accumulate
a large enough sample size to begin to ask this kind of life-history
question," says Alberts. "If you can study the Darwinian fitness
effects of social behavior, that's what we want, but it's taken
a huge investment in time and data." While most research grants
are geared toward short-term projects, she says the recent results
demonstrate the importance of funding long-term projects.
Among the project's mountain of data was a record
of how much time the baboons devoted to two social activities: grooming
and simply being close together. Both activities are considered
indicators of social cohesiveness in many primates, says Silk. "Baboons
tell us this is important, because it's what they do." Grooming,
she adds, is "the most common form of non-aggressive, social interaction,"
occupying up to 10 percent of daylight hours.
Grooming involves such activities as removing ticks or cleaning wounds. And while grooming could have direct benefits -- fewer tick bites should translate to less disease -- it also seems to have indirect benefits. Pet your cat or dog -- and both parties will have reductions in blood pressure.
When the researchers counted how many of the young reached one year of age, they found a noticeable, but not huge, edge among animals whose mothers spent longest in social interactions. And even though these mothers also tended to be dominant females, the higher survival was traceable to the social interaction, rather than dominance, Silk says.
It was, she added, the first proof that social interaction
offers an evolutionary advantage to non-human primates.
In Amboseli, five baboons rest together. One
adult female with a young infant grooms an adult male, while another
adult female rests with an older infant. These intensely social
primates spend almost every waking moment together. Photo
by Susan Alberts
One fun thing about the science journalism biz: you can take a study that required years of careful research, and ask smart questions that will require many more years of research. And that's exactly what we did. Why exactly, we asked Silk, is social support so useful?
First, she admitted ignorance: "We don't exactly know" why social support is helpful. "The great thing about working in the field is that you can see how real life works ... but it's very difficult to tease out the causal processes underlying these effects." On its face, a correlation between sociability and survival does not prove anything about cause.
But then she speculated (proving herself a true Why-Files
type scientist!) that the answer may lie in a mix of two types of
explanation. Social contact could have direct benefits: "You may
be less likely to be preyed upon. Or if you are in a group that
shares the burden of looking for predators, you can feed more efficiently.
Or grooming itself is beneficial. Or maybe if you are the kind of
female who hangs out with others, you more likely to be supported
in a conflict. Or maybe your infant gets protected, or has better
access to resources."
Ride 'em cowgirl! Actually, the young female
baboon at left is grooming an adult female, whose infant is riding
tall in the saddle. Grooming appears to strengthen social bonds.
Photo by Susan Alberts
Grooming could also have indirect benefits,
she adds. "You may be more relaxed, less stressed, and that is generally
good for your health, and your infant's health. Maybe the physiological
benefits of being groomed, reducing heart rate, and increased levels
of endorphins [natural pain killers] are good for your infant."
Since nobody knows exactly why humans get so many benefits from social contact, she is not surprised that the question remains open when the subject shifts to baboons. Mom, you listening?
-- David Tenenbaum
Social Bonds of Female Baboons Enhance
Infant Survival, Joan B. Silk et al, Science, Nov. 17, 2003.