Past research on aging and the life histories of diverse species has shown that sexual reproduction is biologically costly for individuals and tends to decrease lifespan rather than increase it. But a new study by Philip Dammann and Hynek Burda from the University of Duisburg-Essen shows that, in a vertebrate species, the opposite can be true as well.
The authors, studying captive Zambian mole-rats (Cryptomys anselli), analyzed breeding data gathered over the course of more than 20 years. These subterranean, almost-blind, hamster-sized rodents are among the very few mammal species that have adopted a eusocial lifestyle. This means that they live in family groups containing one breeding pair--offspring remain with their parents as (mostly whole-life) helpers--burrowing, foraging, and raising young together. Whereas the breeding pair is sexually active throughout the year, the helpers are sexually quiescent. By comparing the long-term survival of breeders and non-breeders, Dammann and Burda found that the former lived extraordinarily long (up to 20 years) and on average about twice as long as their non-breeding counterparts. The researchers were also able to show that this pattern was not caused by differences in intrinsic biological quality, social rank, or workload between breeders and non-breeders.
These findings provide unexpected new information for understanding the evolution of life histories, and they shed new light on the old question of the connection between sexual activity and aging. Furthermore, as the authors argue, Cryptomys anselli could become a valuable new model organism for the study of the mechanisms that underlie aging, since this species offers the rare opportunity to study differential aging rates among individuals possessing the same genes and experiencing the same environmental conditions, apparently differing only in the aspect of pair-bonding and engaging in sexual activity.
The researchers include Philip Dammann and Hynek Burda of the University Duisburg-Essen in Essen, Germany.
Dammann et al.: "Correspondence: Sexual activity and reproduction delay ageing in a mammal." Publishing in Current Biology 16, R117-118, February 21, 2006. www.current-biology.com