Polygamous baboon fathers get more grandchildren if they spend a little time with their children during their juvenile years, according to research conducted by scientists at Duke and Princeton universities.
The findings, in studies of social groupings of yellow baboons living at the foot of Africa's Mt. Kilimanjaro, were unexpected in "multi-male" animal societies where both genders have multiple partners and mature males were thought to focus their energies almost solely on mating.
"In such societies, the scientific dogma has very much been that males do not contribute to their offspring's fitness," says Susan Alberts, associate professor of biology at Duke. "They're not supposed to be engaged in a level of care that would make any difference."
In a study appearing in the online edition of the Proceedings of the National Academy of Sciences (PNAS), Alberts and her colleagues reported that the more time fathers spent living with their young daughters, the earlier the daughters reached menarche, the onset of menstruation. "A female who can start earlier has a longer reproductive life," explains Alberts, the report's senior author. "So starting out early is good."
The study follows up on a 2003 report by Alberts and others in the journal Nature. That report described evidence that yellow baboon males at the Amboseli basin research site in Kenya could recognize their own offspring and also exhibited paternal care by supporting their own sons and daughters in disputes with other juveniles.
The 2008 PNAS report used thirty years of field observations and genetic data on 118 youthful yellow baboons and their known fathers to assess how paternal presence affected offspring fitness. As the most easily accessible measure of long-term fitness, the researchers investigated how soon a father's offspring reached sexual maturity.
After separating out confounding factors such as the natural fitness advantages children of high-ranking mothers gain in matriarchal baboon societies, the authors found that fatherly presence itself gives offspring a jump-start on reproduction-most strikingly females.
The authors added that "sons also experienced accelerated maturation if their father was present during their immature period, but only if their father was high-ranking at the time of their birth."
They acknowledged that the finding for sons was a "puzzle," but hypothesized that young female and male baboons face different challenges. "For young females, because their major opponents in life are adult females and fellow juveniles, the presence of any adult male may be helpful," Alberts says. "But for maturing sons, it may be that it's not really the females they're dealing with; it's the adult males they have to worry about. And in that case, only the presence of a high-ranking dad would be helpful."
Baboon Quality Time
June 1, 2008