Russell L. Ciochon

Continuity of mammalian fauna over the last 200,000 y in the Indian subcontinent

Significance Mammalian extinction during the past several hundred thousand years has been a major focus for evolutionary biologists, geologists, and archaeologists, often being linked to climate change and human overhunting. Until relatively recently, study has been largely restricted to the Americas, Europe, and Australasia. We present the oldest well-dated sequence of mammalian faunas for the Indian subcontinent, demonstrating continuity of 20 of 21 identified mammals from at least 100,000 y ago to the present. We suggest that, although local extirpations occurred, the majority of taxa survived or adapted to substantial ecological pressures in fragmented habitats. These results complement data from Africa and elsewhere that demonstrate the necessity of a nuanced ecological understanding of such extinctions in different areas of the world. Mammalian extinction worldwide during the Late Pleistocene has been a major focus for Quaternary biochronology and paleoecology. These extinctions have been variably attributed to the impacts of climate change and human interference. However, until relatively recently, research has been largely restricted to the Americas, Europe, and Australasia. We present the oldest Middle–Late Pleistocene stratified and numerically dated faunal succession for the Indian subcontinent from the Billasurgam cave complex. Our data demonstrate continuity of 20 of 21 identified mammalian taxa from at least 100,000 y ago to the present, and in some cases up to 200,000 y ago. Comparison of this fossil record to contemporary faunal ranges indicates some geographical redistribution of mammalian taxa within India. We suggest that, although local extirpations occurred, the majority of taxa survived or adapted to substantial ecological pressures in fragmented habitats. Comparison of the Indian record with faunal records from Southeast and Southwest Asia demonstrates the importance of interconnected mosaic habitats to long-term faunal persistence across the Asian tropics. The data presented here have implications for mammalian conservation in India today, where increasing ecological circumscription may leave certain taxa increasingly endangered in the most densely populated region of the world.

Structure and composition of the Trinil femora: functional and taxonomic implications.

The original hominin femur (Femur I) and calotte discovered at Trinil, Java by Eugene Dubois in 1891/1892 played a key role in the early history of human paleontology by purportedly demonstrating the contemporaneity of archaic cranial form with modern human erect (bipedal) posture. On this basis, both specimens were subsequently assigned to Pithecanthropus erectus, later transferred to Homo erectus. However, chronological and phylogenetic links between the two have been questioned from the beginning. Four additional hominin partial femora (Femora II-V) from Trinil were subsequently described but have played a relatively minor part in evolutionary scenarios. Here we present the results of a new analysis of structural and density characteristics of the Trinil femora obtained using computed tomography. Trinil Femur I shows none of the characteristics typical of early Homo femora from elsewhere in Asia or Africa, including a relatively long neck, increased mediolateral bending rigidity of thexa0mid-proximal shaft, or a low position of minimum mediolateral breath on the shaft. In contrast, Femora II-V all demonstrate features that are more consistent with this pattern. In addition, material density distributions within the specimens imply more recent and less complete fossilization of Femur I than Femora II-V. Thus, it is very likely that Trinil Femur I derives from a much more recent time period than the calotte, while the less famous and less complete Femora II-V may represent H.xa0erectus at Trinil. The morphological variation within the Trinil femora can be attributed to broader changes in pelvic morphology occurring within the Homo lineage between the Early and late Middle Pleistocene.