June 08, 2016

700 thousand year old ancestors of H. floresiensis

Nature 534, 245–248 (09 June 2016) doi:10.1038/nature17999

Homo floresiensis-like fossils from the early Middle Pleistocene of Flores

Gerrit D. van den Bergh, Yousuke Kaifu, Iwan Kurniawan, Reiko T. Kono, Adam Brumm, Erick Setiyabudi, Fachroel Aziz & Michael J. Morwood

The evolutionary origin of Homo floresiensis, a diminutive hominin species previously known only by skeletal remains from Liang Bua in western Flores, Indonesia, has been intensively debated. It is a matter of controversy whether this primitive form, dated to the Late Pleistocene, evolved from early Asian Homo erectus and represents a unique and striking case of evolutionary reversal in hominin body and brain size within an insular environment1, 2, 3, 4. The alternative hypothesis is that H. floresiensis derived from an older, smaller-brained member of our genus, such as Homo habilis, or perhaps even late Australopithecus, signalling a hitherto undocumented dispersal of hominins from Africa into eastern Asia by two million years ago (2 Ma)5, 6. Here we describe hominin fossils excavated in 2014 from an early Middle Pleistocene site (Mata Menge) in the So’a Basin of central Flores. These specimens comprise a mandible fragment and six isolated teeth belonging to at least three small-jawed and small-toothed individuals. Dating to ~0.7 Ma, these fossils now constitute the oldest hominin remains from Flores7. The Mata Menge mandible and teeth are similar in dimensions and morphological characteristics to those of H. floresiensis from Liang Bua. The exception is the mandibular first molar, which retains a more primitive condition. Notably, the Mata Menge mandible and molar are even smaller in size than those of the two existing H. floresiensis individuals from Liang Bua. The Mata Menge fossils are derived compared with Australopithecus and H. habilis, and so tend to support the view that H. floresiensis is a dwarfed descendent of early Asian H. erectus. Our findings suggest that hominins on Flores had acquired extremely small body size and other morphological traits specific to H. floresiensis at an unexpectedly early time.


Nature 534, 249–253 (09 June 2016) doi:10.1038/nature17663

Age and context of the oldest known hominin fossils from Flores

Adam Brumm, Gerrit D. van den Bergh, Michael Storey, Iwan Kurniawan, Brent V. Alloway, Ruly Setiawan, Erick Setiyabudi, Rainer Grün, Mark W. Moore, Dida Yurnaldi, Mika R. Puspaningrum, Unggul P. Wibowo, Halmi Insani, Indra Sutisna, John A. Westgate, Nick J. G. Pearce, Mathieu Duval, Hanneke J. M. Meijer, Fachroel Aziz, Thomas Sutikna, Sander van der Kaars, Stephanie Flude & Michael J. Morwood

Recent excavations at the early Middle Pleistocene site of Mata Menge in the So’a Basin of central Flores, Indonesia, have yielded hominin fossils1 attributed to a population ancestral to Late Pleistocene Homo floresiensis2. Here we describe the age and context of the Mata Menge hominin specimens and associated archaeological findings. The fluvial sandstone layer from which the in situ fossils were excavated in 2014 was deposited in a small valley stream around 700 thousand years ago, as indicated by 40Ar/39Ar and fission track dates on stratigraphically bracketing volcanic ash and pyroclastic density current deposits, in combination with coupled uranium-series and electron spin resonance dating of fossil teeth. Palaeoenvironmental data indicate a relatively dry climate in the So’a Basin during the early Middle Pleistocene, while various lines of evidence suggest the hominins inhabited a savannah-like open grassland habitat with a wetland component. The hominin fossils occur alongside the remains of an insular fauna and a simple stone technology that is markedly similar to that associated with Late Pleistocene H. floresiensis.


No comments: