Evolution of Mothering: How Long Should a Baby Suckle? All primates have drawn-out life histories with long pregnancies and extended suckling. Time devoted to individual offspring more than compensates for limited daily investment in reproduction. A key part of intensive maternal care in primates is frequent suckling on demand, reflected in milk composition. In all these respects, humans are typical primates; but we also have special features, notably in brain development. But how long should a mother suckle her baby? Biological comparisons yield clues to the natural breastfeeding period for which women are adapted."
Dr. Robert Martin is A. Watson Armour III Curator of Biological Anthropology at the Field Museum in Chicago. He has devoted his career to exploring the evolutionary tree of primates, as summarized in his 1990 textbook Primate Origins. Dr. Martin is particularly interested in reproductive biology and the brain, because these systems have been of special importance in primate evolution. His research is based on broad comparisons across primates, covering reproduction, anatomy, behaviour, palaeontology and molecular evolution.
Evolution of modern human beings from extinct nonhuman and humanlike forms. Genetic evidence points to an evolutionary divergence between the lineages of humans and the great apes on the African continent 85 million years ago (mya). The earliest fossils considered to be remains of hominins (members of the human lineage) date to at least 4 mya in Africa; they include the genus Australopithecus and other forms. The next major evolutionary stage, Homo habilis, inhabited sub-Saharan Africa about 21.5 mya. Homo habilis appears to have been supplanted by a taller and more humanlike species, Homo erectus, which lived from c. 1,700,000 to 200,000 years ago, gradually migrating into Asia and parts of Europe. Between c. 600,000 and 200,000 years ago, Homo heidelbergensis, sometimes called archaic Homo sapiens, lived in Africa, Europe, and perhaps parts of Asia. Having features resembling those of both H. erectus and modern humans, H. heidelbergensis may have been an ancestor of modern humans and also of the Neanderthals (H. neanderthalensis), who inhabited Europe and western Asia from c. 200,000 to 28,000 years ago. Fully modern humans (H. sapiens) seem to have emerged in Africa only c. 150,000 years ago, perhaps having descended directly from H. erectus or from an intermediate species such as H. heidelbergensis.