I'm very much a layman in this area. To me, a plausible theory seems to be that a primary advantage of aging is to allow more rapid evolution at the species level, even at the expense of the fitness of individuals. Whole species that can evolve faster to new environments might displace species that have a slower reproductive cycle, or are unable to prioritise for mutations in offspring. The difference in senescence between environments could then be explained by the differences in rates of change of those environments. Perhaps oceans being more stable environments than land. Or tooled/intelligent animals such as humans/elephants more able to adapt to changing environments around them.

I was curious why this theory was not addressed in the paper, what evidence there might be for/against, and pointers to any literature in this area.

Ben