SEX-RATIO AT BIRTH DEVIATIONS IN MODERN VENEZUELA - THE TRIVERS-WILLARD EFFECT

This study evaluates the impact of the Trivers-Willard (T-W) effect on human populations, using demographic data collected from vital regist ration data in Venezuela. The evaluation of the sex ratio at birth (SR B) and of fetal and infant deaths supports the existence of T-W effect in the Venezuelan population in extreme conditions. This T-W effect w as observable in the SRB but not at later ages and is related to the m arital status of the mother. The results indicate that the investment in females associated with environmental adversity is greater than the investment in males associated with good environmental conditions.