DEMOGRAPHIC SENESCENCE AND LIFESPAN HERITABILITY IN A CAPTIVE BABOON COLONY
A. Bronikowski*, L. Martin, A. Comuzzie, M. Mahaney, C. Packer, K.D. Carey, M. Tatar
Southwest Foundation for Biomedical Research, San Antonio, Texas 78245
We report that the baboons of the Southwest Foundation for Biomedical Research demonstrate the demographic and genetic prerequisites to serve as a model nonhuman primate for aging studies. We analyzed thirty years of birth and death records from a captive baboon population residing at the Southwest Foundation for Biomedical Research (SFBR). Female baboons born into the colony and that died of natural causes were included in our analysis (n = 4000). To compare age-specific rates of mortality in this captive colony to those of a population in nature, we analyzed birth and death data on 400 female baboons from Gombe National Park, Tanzania. We found that age-specific juvenile and adult mortality estimates at SFBR are not different than those from the free-living Gombe population (log-rank: P = 0.52; Wilcoxon: P = 0.78). Second, based on parametric model fitting, we found that post-reproductive mortality, as in humans, followed the Gompertz model of steadily increasing mortality with age. Furthermore, maximum likelihood tests indicated that initial mortality is slightly higher in the SFBR population, whereas the rate of increase in age-specific mortality is slightly higher in the Gombe population. We conclude that baboons age demographically in a remarkably similar way in captivity (at SFBR) and in the wild (at Gombe). Furthermore, baboons of SFBR present measurably heritable variance for lifespan. Age at death for males and females (N = 674) that were born into the colony and that died naturally in the colony at an age greater than 5 years were analyzed to partition the variance in lifespan between genetic and environmental effects utilizing their pedigree. From this analysis, we estimated the heritability (i.e., additive genetic variance) of lifespan to be 0.23 (SE = 0.08 P = 0.0003). Sex was not a significant covariate in this analysis, and thus the estimate of lifespan heritability is the same for males and females. Thus, by investigating a large pedigreed captive population, we find that lifespan heritability is both significant and of the same magnitude as has been reported in other model system organisms. We are studying somatic and reproductive senescence in this population, which we believe will be an appropriate and relevant model for human aging.
Key words:
baboon, demographic senescence, lifespan heritability
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