Taphonomy, paleoecology, and hominids of Lainyamok, Kenya

Lainyamok is a hominid fossil and artifact locality west of Lake Magadi in the southern Kenya rift. It is assigned a Middle Pleistocene age, provisionally 0·70-0·56 Ma, based on K-Ar dates, regional association with the Oloronga Beds, and deposition prior to grid faulting in southern Kenya at the end of the Middle Pleistocene. Its fauna is modern compared with that of Olorgesailie Members 1-7 (ca. 0·9-0·7 Ma). From preliminary survey and mapping of surface finds, Lainyamok was initially interpreted as a possible location of hominid butchery activity. Associated clusters of bones of single animals and stone artifacts were found eroding out from a lake margin silt. Stringent criteria are proposed for identifying single animal butchery sites in the prehistoric record. Extensive excavation and geologic fieldwork at Lainyamok now show that none of the criteria for butchery sites is met. Instead, the primary fossiliferous layer (Khaki 2) represents a debris flow which introduced artifacts and possibly some bones into a lake margin setting. Evidence for carnivore damage and accumulation of the majority of excavated bones suggests that hyenas accumulated most of these bones in burrows after deposition of Khaki 2 and prior to deposition of higher strata. In addition to artifacts, a new femur and a previously described set of maxillary teeth indicate the presence of hominids in the area. However, Lainyamok is best considered a locality where evidence of hominid activities is negligible but which enables valuable ecological comparisons to be made to areas where hominids were considerably more active (e.g., Olorgesailie).