The Force of Selection on the Human Life Cycle

Area of Science:

• Evolutionary biology
• Human demography
• Life history theory

Background:

• Human life histories exhibit complex patterns of mortality and fertility.
• Understanding evolutionary pressures requires structured population models.

Purpose of the Study:

• To investigate the force of selection on the human life cycle.
• To identify which life stages are most sensitive to selection.
• To explore factors influencing selection on early survival.

Main Methods:

• Utilized structured population models to analyze human life history evolution.
• Assessed sensitivity of fitness to different vital rates.
• Examined predictors of variation in selection on early survival.

Main Results:

• Pre-reproductive survival, particularly for children aged 0-4, is most sensitive to fitness.
• Human life history creates a "fitness bottleneck" at recruitment due to late reproduction.
• High fertility intensifies selection on early survivorship; high life expectancy reduces it.

Conclusions:

• Selection robustly favors early life survival in humans.
• Antagonistic pleiotropy is expected for traits hindering recruitment.
• Demographic factors like fertility and life expectancy modulate selection on early survival.