Early and Middle Pleistocene environments and hominid biogeography; micromammalian evidence from Kabwe, Twin Rivers and Mumbwa Caves in central Zambia

Kabwe (Broken Hill) has been famous since 1921 for yielding the cranium of Broken Hill Man. The occurrence of micromammals at this site was reported at the time although they were never studied in detail. Twin Rivers was excavated originally by J.D. Clark in 1954 and recently by L.S. Barham. The material discussed comes from the latter excavation. The environmental interpretation agrees with evidence from Mumbwa Caves that all the samples were accumulated under conditions similar to those of the present. This may indicate that Early and Middle Pleistocene Homo spp. only occupied central Zambia during interglacial periods, as they apparently did northern South Africa. Other possibilities are that conditions at low latitudes did not change appreciably between interglacial and glacial periods or that evidence for occupation during the glacial periods must be sought close to permanent water sources where hominids would have sought refuge from drought. It is further postulated that Early and Middle Pleistocene Homo spp. moved among tropical and subtropical savanna habitats, using rivers and lakes, rather than rift valleys per se, as migration routes.