According to a study that has just been published in the journal Proceedings of the National Academy of Sciences (PNAS) , in general, females live 18% longer than males. The team of scientists analyzed the life expectancy in 101 different species, and found that this data was fulfilled in more than 60% of the species studied. In humans, women tend to live 7.8% of men.
“It was already known that women live longer than men, but we were surprised to find that these differences in life expectancy are even more pronounced in wild mammals,” explains Tamás Székely, from the Milner Center for Evolution at the University of Bath and participant in work. “This could be because women are naturally capable of living longer or because female mortality is lower compared to men.”
According to the authors of the work, the reason would be the second: it is not a matter of aging at different speeds, but rather that adult females have less risk of dying than males. This could be due to complex interactions between environmental conditions and the reproductive costs of each sex, but the team will have to test these hypotheses in future investigations.
The example of the lions
The authors explain that, in the case of lions, they live 50% longer than they. At first it was thought that it was due to sexual selection, because males fight each other to get females, but the data analyzed does not support this theory.
“Lionesses tend to live in groups: sisters, mothers and daughters hunt together and take care of each other, whereas adult male lions often live alone or with their brothers and therefore do not have the same support network” , explains the researcher, although this explanation is just a hypothesis that needs to be tested.
“Another possible explanation would be that female survival increases when males assume part of the parental care, as in birds. Giving birth and caring for the pups entails a very high health cost for the females and, therefore, this cost is reduced if both parents collaborate in the rearing of the puppies ”, explains Székely.
Studies in zoos
Another future research will compare the life expectancy data between wild populations and animals that live in captivity and, therefore, do not have to deal with predators and compete for food. This will allow them to measure the extent to which biological differences between the sexes have an effect on life expectancy.
The impact of environmental pathogens, which affect males and females differently and therefore can produce sex differences in life expectancy, could also be studied in this way.
Referencia: Lemaître et al. (2020) “Sex differences in adult lifespan and aging rates of mortality across wild mammals” is published in Proceedings of the Academy of Natural Sciences. DOI: 10.1073/pnas.1911999117
