While roughly the same numbers of boys and girls are born each year, in individual families, some couples have four or more daughters and no sons, and some have all male children and no female children. Recently, U-M researchers have detected a human genetic variant that influences the sex ratio of children. For Michigan News, an evolutionary geneticist and study lead, Jianzhi Zhang, comments on the findings, including a breakdown of what influences the probability of giving birth to a girl instead of a boy.
