Growth and development of Homo erectus

    The Nariokotome youth or “Turkana Boy” is a remarkably complete skeleton found in Kenya in 1984, grouped narrowly within Homo ergaster or broadly within Homo erectus. Compared with the earlier African hominins, the youth shows a larger brain and much longer legs, with a more human-like proportion of his skeleton. From early days after his discovery, the skeleton seemed remarkably long-limbed and large for a juvenile still possessing upper deciduous canines, about comparable to a 11 or 12-year-old boy. The youth, at a stature near 5’3” was already nearly as tall as some estimates for adult Homo erectus. Even odder, an 11-year-old human boy could expect to experience his adolescent growth spurt in the next few years, which would translate to a much larger adult height. But did Homo erectus really grow up in the time frame and manner of living humans?

    I first studied the growth and development of the Nariokotome youth for the 1993 volume “The Nariokotome Homo erectus Skeleton” (edited by Richard Leakey and Alan Walker) KNM15K, but returned to study it again with Christopher Dean of University College London in 2010. We reassessed his dental age (10-10 ½) and bone age (13 ½), finding that this rare combination might occur in obese Westerners or children with endocrinopathy, but would be particularly unexpected in a lean tropical adolescent.  Even more telling, micro-anatomical surface features show that his teeth formed more quickly than in humans and that actual age at death was much younger—likely between 7.6 and 8.8 years. At this age, his size and development cannot be forced onto a human growth chart. We concluded that his pace of growth was more rapid than that of modern humans, marginally slower than that of a chimpanzee, and that it is unlikely that the modern human adolescent growth spurt existed at the time. The complete study appears in “The First Humans”, edited by Fred Grine, John Fleagle and Richard Leakey (2009).