The co-evolution of the ageing process, lifespan, and intergenerational transfers

Hillard S. Kaplan, University of New Mexico
Michael D. Gurven, University of California, Santa Barbara
Jeff Winking, University of New Mexico
Paul Hooper, University of New Mexico
Jon Stieglitz, University of New Mexico
Katherine Hinde, University of California, Santa Barbara
Daniel Eid R, Universidad Mayor San Simon, Bolivia

This paper builds on a theory that links intergenerational transfers to the aging process. It presents empirical data to evaluate the hypothesis that the modal age of death in traditional human populations, 70, is very close to the median age at which intergenerational transfers become negative. We analyze data on economic transfers, aging and disability, and demography collected with Tsimane forager-horticulturalists. The median age at which net transfers become negative is within 2-3 years later of the modal age of death. The decrease in net transfers with age is directly linked to functional changes in the ability to work due to the aging process itself. Finally, the data show that the vast majority of Tsimane children born have at least two grandparents alive at the time, and do receive positive economic transfers from them. By the age net transfers become negative, older people have very few young grandchildren left to support.