Eric R. Lucas and Laurent Keller
We know that social interactions are essential for humans to live a full and healthy life, but does social life increase health and lifespan in other species as a general rule? This question can be asked on two levels. First, at the level of the individual, do more socially-connected individuals live longer? Our review of the literature suggests that the answer is yes, but only in species that normally live in relatively large groups (more than about 8 individuals on average), and even then only sometimes. This might be because increased social contact is only beneficial in species that are used to living in large social groups. The second question is, at the level of the species, do more social species tend to live longer than less social species, or solitary species? Here, the answer appears to be no in most cases. The exception seems to be in species known as “co-operative breeders”, where a few “breeder” individuals reproduce, while other individuals, known as “helpers” or “workers” help the breeders in rearing the young. In mammal and insect co-operative breeders, the breeders appear to live longer than individuals in non-cooperatively-breeding species, perhaps thanks to the help and care that they receive from the helpers. How the lifespan of helpers compares with individuals from solitary species remains to be determined.
The breeders in cooperative species can live an extremely long time compared to their solitary counterparts, leading to research into the mechanisms by which these lifespans are extended in the hope of better understanding our own patterns of ageing. The best example of this is the naked mole rat, a subterranean rodent which can live up to 30 years, and which has been shown to suffer from extremely low rates of cancer compared to mice, which can live up to four years at the most. The molecular basis for this cancer avoidance is only beginning to be elucidated.