Growth, development, and life history throughout the evolution of Homo

For over a century, paleoanthropologists have listed the presence of prolonged periods of gestation, growth, and maturation, extremely short interbirth intervals, and early weaning among the key features that distinguish modern humans from our extant ape cousins. Exactly when and how this particular scheduling of important developmental milestones-termed a "life history profile"-came to characterize Homo sapiens is not entirely clear. Researchers have suggested that the modern human life history profile appeared either at the base of the hominin radiation (ca. 6 Ma), with the origins of the genus Homo (ca. 2.5 Ma), or much later in time, perhaps only with H. sapiens (ca. 200-100 Ka). In this short review, evidence of the pace of growth and maturation in fossil australopiths and early members of Homo is detailed to evaluate the merits of each of these scenarios. New data on the relationship between dental development and life history in extant apes are synthesized within the context of life history theory and developmental variation across modern human groups. Future directions, including new analytical tools for extracting more refined life history parameters as well as integrative biomechanical and developmental models of facial growth are also discussed.