Growth and Development of the Nariokotome Youth, KNM-WT 15000

Abstract

A substantial number of the large, slow-growing fauna on several continents were famously lost in the Pleistocene extinctions. At present, many slow-growing, long-lived mammals are threatened with extinction all over the world. Rhinos, elephants, chimpanzees, orangutans, and gorillas all make an enormous investment in their single offspring, taking years to raise one to independence. Recovery from population downturns is always diffi cult and sometimes impossible. Large investments in a single offspring, in theory, produce high quality offspring that may be larger, smarter, or more social, but slow maturers risk dying before reproducing. Of all these species, humans are the slowest to begin reproducing. In recent years it has become clear that human growth and development, like human life history in general, was not present in australopiths (see Kuykendall, 2003 for a recent review). Evidence suggests, on the contrary, that much of what makes our life history unique took shape during the evolution of the genus Homo. Much of our evidence comes from the study of incremental records of daily growth preserved in teeth (see Dean, 2006), and some from correlative studies of life history in living primates (Smith, 1989, 1991). Given time and judicious use of some partially destructive analytical techniques, it seems likely that we will eventually be able to retrieve a time scale of dental maturation for each species within the Homininae and thus be able to reconstruct the general pace of maturation for each. In this effort, even single broken or sectioned teeth can make a contribution to knowledge. Even so, the occasional rare fossil of a more complete juvenile offers the chance to attempt a more complete reconstruction of maturation, or to ask questions that go beyond time scale alone. The juvenile male Homo erectus skeleton of Nariokotome (KNM-WT 15000) is one of these.