Female infanticide and human sex ratio evolution

Area of Science:

• Evolutionary biology
• Human population genetics
• Behavioral genetics

Background:

• Cultural preferences for male offspring have been documented in various human populations.
• These preferences can potentially influence demographic patterns, including the sex ratio at birth.
• Previous theoretical models have yielded conflicting predictions regarding the evolutionary consequences of such preferences.

Purpose of the Study:

• To investigate the impact of a preference for male children on the evolution of the human sex ratio using a genetic model.
• To reconcile contradictory findings in previous studies on this topic.

Main Methods:

• Development of a genetic model incorporating a preference for male children.
• Simulation of different decision rules for determining the fate of infants, specifically focusing on the killing of daughters.
• Analysis of the model's output to determine the resulting sex ratio.

Main Results:

• The model demonstrates that the practice of killing infant daughters can lead to a skewed human sex ratio.
• The direction of the sex ratio bias (either towards males or females) is contingent upon the specific decision-making rules governing child survival.
• This finding provides a unifying explanation for previously observed contradictory results in sex ratio evolution studies.

Conclusions:

• A preference for male children, when coupled with infanticide, can significantly alter the human sex ratio.
• The evolutionary outcome is sensitive to the behavioral strategies adopted by the population.
• This study offers a resolution to long-standing debates regarding the evolutionary dynamics of sex ratio determination under cultural pressures.