The Interval between Pregnancies and the Outcome of Subsequent Births

Is there a “natural” interval between pregnancies in humans? Our nearest animal relatives, the chimpanzees and gorillas, breast-feed their offspring for long periods, and the median time from the birth of one offspring to the conception of the next is approximately 3.5 to 5 years.1 The median birth-to-conception interval among women in less developed countries who breast-feed their infants is approximately three years,1 but the interval might be shorter in women from better-nourished populations, even if their practices of breast-feeding and sexual intercourse are similar to those of women in the less developed areas. Some groups of people have cultural . . .