All round the world, women live longer than men. Why they should do so is not immediately obvious. Most students of ageing agree that an animal's maximum lifespan is set by how long it can reasonably expect to escape predation, disease, accident and damaging aggression by others of its kind. If it will be killed quickly anyway, there is not much reason for evolution to divert scarce resources into keeping the machine in tip-top condition. Those resources should, instead, be devoted to reproduction.
The paper, Ecological correlates of extra-group paternity in mammals, is rather more technical: Extra-group paternity (EGP) can form an important part of the mating system in birds and mammals. However, our present understanding of its extent and ecology comes primarily from birds. Here, we use data from 26 species and phylogenetic comparative methods to explore interspecific variation in EGP in mammals and test prominent ecological hypotheses for this variation. We found extensive EGP (46% of species showed more than 20% EGP), indicating that EGP is likely to play an important role in the mating system and the dynamics of sexual selection in mammals. Variation in EGP was most closely correlated with the length of the mating season. As the length of the mating season increased, EGP declined, suggesting that it is increasingly difficult for males to monopolize their social mates when mating seasons are short and overlap among females in oestrus is likely to be high. EGP was secondarily correlated with the number of females in a breeding group, consistent with the idea that as female clustering increases, males are less able to monopolize individual females. Finally, EGP was not related to social mating system, suggesting that the opportunities for the extra-group fertilizations and the payoffs involved do not consistently vary with social mating system.
Live fast, love hard, die young |
