Human sex ratio as it relates to caloric availability

Area of Science:

• Human biology
• Demographics
• Nutritional science

Background:

• The human sex ratio at birth is generally stable but can be influenced by various factors.
• Understanding environmental influences on human reproductive outcomes is crucial for population studies.

Purpose of the Study:

• To investigate the correlation between per capita caloric availability and human sex ratios at birth across nations.
• To explore potential adaptive mechanisms influencing human sex determination based on resource availability.

Main Methods:

• Cross-national analysis correlating national food supply data with recorded sex ratios at birth.
• Statistical examination of the relationship between changes in caloric availability and corresponding shifts in sex ratios.

Main Results:

• A significant positive correlation was found between per capita caloric availability and the proportion of male births.
• Changes in national caloric availability were associated with corresponding alterations in the sex ratio at birth.
• Evidence suggests adaptive sex ratio biasing in human populations.

Conclusions:

• Human sex ratios at birth appear to be sensitive to nutritional status at a population level.
• Nutritional deficiencies and associated stressors may increase male embryo/fetus mortality, influencing the observed sex ratio.
• These findings support the hypothesis of adaptive sex ratio adjustment in response to environmental conditions.