> That's around 20% of the population in total (assuming 50 / 50 chance of male and female birth)
Author mentions that primitive societies living in abundance don't have 50/50 most likely to female infanticide. If low number of working women can provide resources it's more important to have more male warriors to defend the group. Excess of women would just get stolen by another group if men numbers in the group got too low.
I think this next post contains many more interesting observations than this one.
In 1970 anthropologist William Divale compiled sex ratio data from 112 primitive societies. He found that among societies practicing war, sex ratios were on average very male-skewed among children and much less male-skewed among adults. The probable explanation Divale found was sex-biased infanticide.
Author mentions that primitive societies living in abundance don't have 50/50 most likely to female infanticide. If low number of working women can provide resources it's more important to have more male warriors to defend the group. Excess of women would just get stolen by another group if men numbers in the group got too low.