Evidence of adaptive intergenerational sex ratio adjustment in contemporary human populations.

Using the abrupt decline in sex ratio at birth in China during and immediately after the 1959-1961 Great Leap Forward Famine in China as a natural experiment, this study conducts difference-in-differences analysis to test the hypothesis that changes in the sex ratio at birth of the maternal generation can produce adaptive changes in the sex ratio at birth of the offspring generation toward the opposite direction, which was derived from the developmental and evolutionary psychological literature on female reproductive strategy. The results show that, after controlling for sex-selective abortion, the decline in the sex ratio at birth in 1962-1964 caused a substantial increase in the sex ratio at birth among children whose mothers were born in 1963. Such finding suggests the presence of adaptive intergenerational sex ratio adjustment in humans.