HOLOCENE PALEOENVIRONMENTAL CHANGE IN THE KENYAN CENTRAL RIFT AS INDICATED BY MICROMAMMALS FROM ENKAPUNE-YA-MUTO ROCKSHELTER

An assemblage of micromammals, recovered from the Holocene levels of a rockshelter at 2400 m in the montane forest of the Mau Escarpment, we re examined with the goal of testing and contributing to prior reconst ructions of paleoenvironments in the Central Rift Valley of Kenya. Spe cies representation in the assemblage is consistent with a drying of t he Rift Valley lakes in the middle Holocene and suggests a decrease in forest accompanied by expanding grasslands near the site. Changes in the abundance of grassland species suggests an increase in the frequen cy of fires, probably the result of pastoral burning. The body size of the root rat (Tachyoryctes splendens) decreases from the early Holoce ne to the middle Holocene, and this may indicate increasing aridity or increasing temperature. We compare measures of species diversity (num ber of taxa, species richness, and the Shannon diversity index) for bo th micromammals and macromammals since species diversity may change wi th paleoenvironmental change. The macromammals show no changes in spec ies diversity that are assignable to paleoenvironmental change, while the micromammals show a trend toward decreasing diversity from the ear ly to middle Holocene, and then show an increase in diversity during t he peak of the middle Holocene dry phase, though sample size effects m ay be confounding the patterning. (C) 1994 University of Washington.