Original Research Article
Mortality and fertility rates in humans and chimpanzees: How within-species variation complicates cross-species comparisons
Article first published online: 11 FEB 2009
Copyright © 2009 Wiley-Liss, Inc.
American Journal of Human Biology
Special Issue: Trade-Offs in Female Life Histories: Integrating Evolutionary Frameworks
Volume 21, Issue 4, pages 578–586, July/August 2009
How to Cite
Hawkes, K., Smith, K. R. and Robson, S. L. (2009), Mortality and fertility rates in humans and chimpanzees: How within-species variation complicates cross-species comparisons. Am. J. Hum. Biol., 21: 578–586. doi: 10.1002/ajhb.20890
- Issue published online: 9 JUN 2009
- Article first published online: 11 FEB 2009
- Manuscript Accepted: 21 DEC 2008
- Manuscript Revised: 3 DEC 2008
- Manuscript Received: 10 SEP 2008
A grandmother hypothesis may explain why humans evolved greater longevity while continuing to end female fertility at about the same age as do the other great apes. With that grandmother hypothesis in mind, we sought to compare age-specific mortality and fertility rates between humans and chimpanzees, our closest living relatives, and found two puzzles. First, we expected that lower adult mortality in humans would be associated with slower senescence, but the rate of chimpanzee demographic aging falls within the human range. Second, we expected declines in age-specific fertility to be similar in the two species but instead of falling in the thirties as it does in women, fertility remains high into the forties in some chimpanzee populations. We report these puzzles using data from nine human populations and both wild and captive chimpanzees, and suggest that systematic differences in the heterogeneity of surviving adults may explain them. Am. J. Hum. Biol., 2009. © 2009 Wiley-Liss, Inc.