Five years of Homo floresiensis

Since Homo floresiensis was first described in October 2004 there has been a lively debate over its status. Is it a late surviving species of early Homo or merely a modern individual afflicted with disordered growth and one of the many syndromes resulting in microchephaly? Recently the discovery team has published a series of articles providing detailed descriptions of the hominin material, its geomorphological context, and the associated archaeology and faunal material (Morwood and Jungers: J Hum Evol 57 (2009) 437-648). In addition, other researchers have put forward new hypotheses for possible pathologies including Laron's Syndrome and Myxoedematous Endemic (ME) Cretinism. Here I review this new information and conclude that the evidence supports the hypothesis that Homo floresiensis is a late-surviving species of early Homo with its closest morphological affinities to early African pre-erectus/ergaster hominins. Although this hypothesis requires fundamental paradigm changes in our understanding of human evolution, it provides a more economical explanation for H. floresiensis than do the alternatives. None of the current explanations for microcephaly and disordered growth account for the range of features observed in H. floresiensis. Neither do they provide explanations for why a pathological condition in modern humans would mimic so closely the morphology observed in earlier hominins. This conclusion is based on the current evidence for H. floresiensis and on the particular pathological explanations that have appeared in the literature. There is no doubt that controversy over H. floresiensis will continue until new and conclusive evidence is available to settle the debate one way or another.