Dr. Katherine A. Dettwyler, PhD, associate professor of anthropology and nutrition at Texas A&M University, has spent a career studying breastfeeding. As coeditor of Breastfeeding: Biocultural Perspectives, and researcher on milk composition and weaning, Dettwyler has concluded one thing for sure: Most children in America are weaned from the breast too early. Way too early.
In Breastfeeding: Biocultural Perspectives, Dettwyler wrote about the natural age of weaning for humans, meaning the length of time humans would likely nurse if cultural expectations did not interfere.
In comparing humans to other primates, research showed that humans' natural age of weaning is a minimum of two and a half years and a maximum of between six and seven years. Researchers compared things such as the age of sexual maturity; the age of the eruption of permanent molars; the time when children quadrupled their birthweight; and the length of gestation.(4) In every other primate, nursing continues for years, not just months.
According to Dettwyler, "The very word infant in zoological terms refers to the time between birth and the eruption of the first permanent molars. " Dettwyler further emphasizes, "The research looking at weaning time in primates and dental eruption shows that breastfeeding ends when infancy ends, when the first permanent molars are erupting. In humans, that happens between 5.5 and 6.5 years."