Fig. 7.

Stabilizing selection of short lifespan setpoint and a potential scenario of lifespan shortening. The mechanism of stabilizing selection described in Fig. 4f is schematically depicted in the upper-left corner. In the lower-right corner is demonstrated a potential scenario of the shorter lifespan evolution in the population, where a longer lifespan setpoint initially prevails. Short-lived variants are persisting in such a population under conditions of high extrinsic mortality or prevalence of sterilizing pathogens. If such a population undergoes a dramatic decline (e.g., due to epidemics of sterilizing sexually transmitted diseases), the fragmentation of the range leads to the establishment of sub-populations with high founder effects. Thus, the pure populations of short-lived individuals can emerge, bringing the model to the scenario of competition described in Fig. 4f.