Abstract
Homo floresiensis is an extinct, diminutive hominin species discovered in the Late Pleistocene deposits of Liang Bua cave, Flores, eastern Indonesia. The nature and evolutionary origins of H. floresiensis’ unique physical characters have been intensively debated. Based on extensive comparisons using linear metric analyses, crown contour analyses, and other trait-by-trait morphological comparisons, we report here that the dental remains from multiple individuals indicate that H. floresiensis had primitive canine-premolar and advanced molar morphologies, a combination of dental traits unknown in any other hominin species. The primitive aspects are comparable to H. erectus from the Early Pleistocene, whereas some of the molar morphologies are more progressive even compared to those of modern humans. This evidence contradicts the earlier claim of an entirely modern human-like dental morphology of H. floresiensis, while at the same time does not support the hypothesis that H. floresiensis originated from a much older H. habilis or Australopithecus-like small-brained hominin species currently unknown in the Asian fossil record. These results are however consistent with the alternative hypothesis that H. floresiensis derived from an earlier Asian Homo erectus population and experienced substantial body and brain size dwarfism in an isolated insular setting. The dentition of H. floresiensis is not a simple, scaled-down version of earlier hominins.
Highlights
Previous studies showed that Homo floresiensis exhibits unusually small body and brain sizes for a Late Pleistocene Homo [1], a H. erectus-like cranial shape [2,3], an Australopithecus-like upper vs. lower limb proportion [4,5,6,7], and other primitive, advanced, and unique skeletal features [8,9,10,11,12,13,14]
These include the claimed two major ancestral candidates for H. floresiensis (H. habilis and early Javanese H. erectus). We focused on these Early Pleistocene samples to investigate the evolution of H. floresiensis because of its generally primitive cranial and other skeletal morphology [2,10,11,13,14,17], with the expectation that larger-brained hominins could not be the ancestor of this small-brained species [25], as well as the evidence for the presence of hominins on Flores ~1.0 Ma [26]
Many of the H. floresiensis teeth are within the smaller range of variation exhibited by the global H. sapiens sample
Summary
Previous studies showed that Homo floresiensis exhibits unusually small body and brain sizes for a Late Pleistocene Homo [1], a H. erectus-like cranial shape [2,3], an Australopithecus-like upper vs. lower limb proportion [4,5,6,7], and other primitive, advanced, and unique skeletal features [8,9,10,11,12,13,14]. Researchers agree that this unique mosaic has significant evolutionary meaning, but disagree on what it is. There is a claim that the mesiodistally elongated P3 of H. floresiensis represents a very primitive hominin condition not seen in H. erectus [15], but more detailed analyses of this and other dental traits are needed to assess its taxonomic affinity [24]
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