[Dysart]

Absolute nonsense. If the average life span had been 25 years, a figure which seems to be way too low, according to the authors the average longevity would then have jumped up to 100.

No, the incidence of longevity quadrupled, not the average lifespan.

[Dysart]

The American team believes there had to be a distinct evolutionary advantage to large numbers of people growing older, which in turn enabled still more of our ancestors to live longer.