Baboon brawls bring out fatherly bonds
By Steven Schultz
Princeton NJ -- The image of the dad who sticks up for his children on the playground may grow out of a parenting instinct that extends further back in primate evolution than previously believed.
A study published Sept. 11 in the journal Nature has shown that male baboons in Kenya commonly identify and care for their own genetic offspring, despite the mothers having mated with several different males.
From 1999 to 2002, researchers from Princeton and Duke universities, the University of California-Los Angeles and Kenya observed male baboons intervene in fights involving juveniles and noted which young one received favored treatment. They also conducted genetic testing on fecal samples from the baboons and established definitive family lineages. The researchers found that nearly all males were two to 10 times more likely to intervene on behalf of their own young as opposed to those of other fathers.
"The tendency of dads to help their own offspring runs quite deep in our primate heritage," said Jeanne Altmann, a Princeton professor of ecology and evolutionary biology and co-author of the study.
The finding runs counter to the standard belief that, although males engage in some caregiving, it was not focused on their own offspring. Baboons live in multi-female groups with adult males moving from one group to another. Males and females do not form permanent bonds, and females mate with multiple males around the time they conceive an infant. Scientists believed that males could not tell which juveniles were biologically their own and that, when they engaged in caregiving, it was probably in an effort to win a new mate. Now researchers believe the caregiving runs along family lines.
"Researchers assumed that males' paternal relatedness was not important, that dads didn't matter," said Altmann, who joined the Princeton faculty in 1998 after 28 years at the University of Chicago. "That belief was conveniently abetted by a lack of data."
Until recently, biologists had no widely useful way to determine the paternity of primate offspring. In the late 1990s, researchers at Duke led by Susan Alberts, a co-author of the study, developed a technique for making DNA fingerprints from fecal samples. Previously, the only way to obtain a DNA sample was to anesthetize the animals and take a blood sample, which was too disruptive for widespread use.
The researchers used genetics to establish paternity for 75 young baboons, which were part of a population that Altmann and colleagues have studied continuously since 1971. They also had detailed records of the females with whom the males had mated. In some cases, the males intervened in fights between juveniles from two mothers who had both mated with the male, but only one of the juveniles was truly his offspring. In those cases, the choice of which juvenile to support was less consistent, but still favored the biological offspring to a statistically significant degree.
The results raise the question of how male baboons distinguish their offspring from those of other males who mated with the same females, Altmann said. Their well-developed discernment suggests that baboons do more than just keep track of their mating, she said. The baboons may respond to cues that come directly from each other's genetic makeup, such as individual smells, but figuring out the exact mechanism will become a major area of investigation, she said.
Another implication of the work is that the protection of individual males may be more important to conservation efforts than previously thought for baboons and other multi-male societies. The more refined an animal's caregiving, the more likely it is that the caregiving is important to the well-being of the animal population. "The social structure has profound importance for the survival of groups," Altmann said, noting that among elephants and mountain gorillas the loss of a single animal can decimate an entire group. "The fact that dads are important even in complex groups suggests that they too may be vulnerable to disruption."
The research was a collaboration between Altmann and Alberts as well as Jason Buchan, a postgraduate fellow in Alberts' lab at Duke, and Joan Silk of UCLA. The researchers also worked with the Kenyan Institute of Primate Research and the Brookfield Zoo of Illinois.
The research was conducted in Kenya's Amboseli National Park at the foot of Mount Kilimanjaro, where Altmann has conducted field work since 1963. The work was supported by grants from the National Science Foundation, the Chicago Zoological Society, the L.S.B. Leakey Foundation and the National Geographic Society.