Abstract
Western Kenya is well known for abundant early Miocene hominoid fossils. However, the Wasiriya Beds of Rusinga Island, Kenya, preserve a Pleistocene sedimentary archive with radiocarbon age estimates of >33-45 ka that contains Middle Stone Age artifacts and abundant, well-preserved fossil fauna: a co-occurrence rare in eastern Africa, particularly in the region bounding Lake Victoria. Artifacts and fossils are associated with distal volcanic ash deposits that occur at multiple localities in the Wasiriya Beds, correlated on the basis of geochemical composition as determined by electron probe microanalysis. Sediment lithology and the fossil ungulates suggest a local fluvial system and associated riparian wooded habitat within a predominantly arid grassland setting that differs substantially from the modern environment, where local climate is strongly affected by moisture availability from Lake Victoria. In particular, the presence of oryx (Oryx gazella) and Grevy's zebra (Equus grevyi) suggest a pre-Last Glacial Maximum expansion of arid grasslands, an environmental reconstruction further supported by the presence of several extinct specialized grazers (Pelorovis antiquus, Megalotragus sp., and a small alcelaphine) that are unknown from Holocene deposits in eastern Africa. The combination of artifacts, a rich fossil fauna, and volcaniclastic sediments makes the Wasiriya Beds a key site for examining the Lake Victoria basin, a biogeographically important area for understanding the diversification and dispersal of Homo sapiens from Africa, whose pre-Last Glacial Maximum history remains poorly understood.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 657-671 |
| Number of pages | 15 |
| Journal | Journal of Human Evolution |
| Volume | 59 |
| Issue number | 6 |
| DOIs | |
| State | Published - Dec 2010 |
Bibliographical note
Funding Information:The research described here was conducted under research permit NCST/5/002/R/576 issued to C.Tryon by the Republic of Kenya, and others issued to K. McNulty, W. Harcourt-Smith, and H. Dunsworth, as well as an exploration and excavation license issued by the National Museums of Kenya (NMK). Our fieldwork in Kenya is made possible through the support of the NMK (particularly Drs. Emma Mbua, Frederick Kyalo Manthi, and Isaya Onjala) and the British Institute in East Africa, with funding provided by the National Science Foundation ( BCS-0841530 and BCS-0852609 ), the Leakey Foundation , the National Geographic Society's Committee for Research and Exploration ( 8762-10 ), New York University , Baylor University , and the University of Minnesota . We thank the NSF-Arizona AMS Facility, and particularly Greg Hodgins and Jay Quade for helpful discussions on radiocarbon chronology, Craig Rasmussen for the XRD analyses, and Andy Cohen for comments on eastern African paleoclimates. Jerry Delaney provided valuable assistance with the electron microprobe, Mike Rampino helped with the petrography, and Bob Hershler of the National Museums of Natural History’s Invertebrate Zoology Department and Ben Rowson of the National Museum of Wales helped to indentify the gastropods. The Rusinga Island Lodge, and Matthew Eregae Macharwas, Bernard ‘Kanyenze’ Ngeneo, Joshua Siembo, and particularly Jared Olelo, made fieldwork on Rusinga pleasant and always entertaining. Comments by Stanley Ambrose, Lindsay McHenry, an anonymous reviewer, the associate editor and David Begun substantially improved the manuscript. The tephrostratigraphic work presented here is a contribution towards meeting objective three of the INTREPID project of INQUA’s International focus group on tephrochronology and volcanism.
Keywords
- Aridity
- Lake Victoria
- Middle Stone Age
- Pleistocene
