Birth order coital rates, polygyny, stress, and the secondary sex ratio: A reply to James

摘要

Between 1896 and 1988 the Havasupai Indians produced 677 births. The sex ra- tio among those births was 0.51 male. While there were secular variations in the sex ratio at birth and, consequently, in adult sex ratios, the secondary sex ratio correlated negatively with birth order in a marital union throughout the period (Martin, 1994). Hence, secondary sex ra- tios remained high among early births when the secondary sex ratio as a whole was declining as they did when adult sex ratios were high.