To test the hypothesis that a characteristic infant-care pattern existed during most of human history, contemporary hunter-gatherers in a representative sample of world cultures were examined. Numerically coded measures of infant care revealed a uniform pattern. Mothers are the principal caregivers, providing extensive body contact day and night and prolonged breast-feeding. When not carried, the baby of hunter-gatherers has complete freedom of movement. Care is consistently affectionate, with immediate nurturant response to crying. Nonetheless, in most groups, children achieve early independence and by 2 to 4 years spend more than half the time away from the mother. In the United States this pattern of carrying that endured for one to three million years has been replaced by one resembling nesting or caching. Infants spend little time in body contact with caregivers and their movements are restricted by playpens, high chairs, or cribs. Of the minority who are breast-fed, half are weaned within a few weeks. Separate sleeping arrangements and delayed response to crying are regularly recommended. These remarkable transformations may profoundly alter infant development and maternal involvement.