The Australopithecines – An Extinct Group of Human Ancestors: My Scientific Interest in South Africa

I introduce the subject of my research interest in South Africa - the australopithecines - a group of bipedal, small-brained and large-toothed creatures from the Plio-Pleistocene, from which the human genus arose. I then briefly discuss various topics of my research, concerning: (1) Taxonomic status and morphological description of the extinct human relative from the Kromdraai site (Australopithecus robustus); (2) Graphic reconstruction of the partial skull from Kromdraai - specimen numbered TM 1517; (3) Assessment of size sexual dimorphism of the South African australopithecines (Australopithecus robustus and Australopithecus africanus), which, in terms of facial features, was pronounced - being almost gorilla-sized; (4) Social behavior of a fossil hominid species from around 2 million years ago, which, in terms of the social structure, was most likely a multimale-multifemale one; and (5) An event from the history of paleoanthropology, concerning the content of the 1924/25 photographs of the Taung Child (Australopithecus africanus) - the first australopithecine skull discovered.

Australopithecus robustus societies – one-male or multimale?

Determining the sex of individual specimens is important in estimating the degree of sexual dimorphism. Sexual dimorphism, in turn, provides clues for reconstructing the social organisation and mating systems of extinct species. In an article published in Science, Lockwood et al. (Lockwood CA, Menter CG, Moggi-Cecchi J, Keyser AW. Extended male growth in a fossil hominin species. Science. 2007;318:1443–1446.) suggested an uneven sex ratio (in favour of males) for the known individuals of the South African Pleistocene hominid, Australopithecus robustus, and claimed evidence of an extended period of growth (delayed maturity) for the males of this species. They concluded that this finding, combined with estimates of sexual size dimorphism, suggests a polygynous reproductive strategy, and a social system similar to that of silverback gorillas (i.e. one-male harems). On re-examination of these claims, and based on further analysis, I agree with Lockwood et al. that morphologically A. robustus exhibits an increased (almost gorilla-like) level of facial dimorphism, but propose using an alternate (clustering) technique for grouping the specimens of highly dimorphic species into sexes, and argue that their pronouncements regarding a polygynous social structure of these early hominids are inconclusive. I contend instead that the habitat occupied by this species suggests rather that a one-male harem social structure would have been counterproductive.