Roy M. Huffington Department of Earth Sciences

Lothagam is a richly fossiliferous late Miocene site near the western shore of Lake Turkana, northern Kenya. This site has yielded a diverse fauna documenting a chronological interval poorly known from elsewhere in Africa. Lothagam was first collected by an American research group in the late 1960s and early 1970s. Field studies by the National Museums of Kenya between 1989–1993

Test excavations conducted at Drotsky's Cave have provided important new information on the paleoenvironment and archaeology of the western Kalahari desert during the late and terminal Pleistocene. An occupation layer dated to the terminal Pleistocene was rich in Late Stone Age artefacts, pieces of ostrich egg shell, the remains of carnivorous bullfrogs, springhare, and other fauna. A detailed sediment study, along with the evidence of Angoni vlei rat, climbing mouse, an aquatic Xenopus frog, and side neck turtle confirms that conditions were for the most part, substantially more moist than at present between approximately 30,000 and 11,000 years ago. Analysis of a diatom assemblage dated to the terminal Pleistocene implies that the currently dry Gcwihaba Valley was most likely flowing for much of the year. Our evidence supports findings made at other localities in the Kalahari documenting the existence of especially moist conditions during the terminal Pleistocene.

Although Lagomorpha (rabbits, hares and pikas) have a long evolutionary history in Eurasia and Africa, including primitive genera of Eurasia historically considered assignable at the family level to Leporidae, the predecessors of modern rabbits were absent throughout this vast region for most of the Miocene until late in that epoch. During the early and middle Miocene, crown group Leporidae differentiated in North America, then dispersed to northern Asia in the late Miocene around 8 Ma (million years before present) and afterward. They then spread widely and apparently rapidly throughout Eurasia, reaching South Asia by 7.4 Ma and penetrating Africa about 7 Ma. bs_bs_banner

Carbon and oxygen isotope compositions of pedogenic carbonate preserved in paleosols have been used extensively to reconstruct ancient environmental conditions. One concern is that pedogenic carbonate precipitated in association with a limestone parent material may include a contribution from inherited detrital (lithogenic) marine calcite, thus compromising interpretations of stable-isotope compositions. To investigate the impact of lithogenic calcite on environmental interpretations using paleosols, we measured stable-isotope ratios in pedogenic carbonates and coexisting soil organic matter (SOM) in modern Vertisols (fine, smectitic, thermic, Udic Haplusterts) from Riesel, Texas (Heiden series) and Zabcikville, Texas (Houston Black series) forming on Cretaceous chalk deposits. The pedogenic and lithogenic components in the Heiden series soil at Riesel were identified using micromorphology and cathodoluminescence (CL), which showed incorporation of luminescent marine allochems (i.e., foraminifera, mollusks) into hard nodules and soft powdery pedogenic masses. Additionally, micromorphology showed evidence of meteoric recrystallization of the allochems.

The lineage of apes and humans (Hominoidea) evolved and radiated across Afro-Arabia in the early Neogene during a time of global climatic changes and ongoing tectonic processes that formed the East African Rift. These changes probably created highly variable environments and introduced selective pressures influencing the diversification of early apes. However, interpreting the connection between environmental dynamics and adaptive evolution is hampered by difficulties in locating taxa within specific ecological contexts: time-averaged or reworked deposits may not faithfully represent individual palaeohabitats. Here we present multiproxy evidence from Early Miocene deposits on Rusinga Island, Kenya, which directly ties the early ape Proconsul to a widespread, dense, multistoried, closed-canopy tropical seasonal forest set in a warm and relatively wet, local climate. These results underscore the importance of forested environments in the evolution of early apes.

The effect of changing palaeoclimate and palaeoenvironment on human evolution during the
Pleistocene is debated, but hampered by few East African records directly associated with
archaeological sites prior to the Last Glacial Maximum. Middle to Late Pleistocene deposits on
the shoreline of eastern Lake Victoria preserve abundant vertebrate fossils and Middle Stone Age
artefacts associated with riverine tufas at the base of the deposits, which are ideal for palaeoenvironmental reconstructions. New data from tufas identified on Rusinga Island and on
the mainland near Karungu, Kenya are provided from outcrop, thin-sections, mineralogical,
stable isotopic and U-series dating analyses. Tufa is identified at four sites: Nyamita (94.0 ± 3.3
and 111.4 ± 4.2 ka); Kisaaka, Aringo (455 ± 45 ka); and Obware. The age ranges of these tufa
deposits demonstrate that spring-fed rivers were a recurrent, variably preserved feature on the
Pleistocene landscape for ca 360 kyr. Poor sorting of clastic facies from all sites indicates flashy,
ephemeral discharge, but these facies are commonly associated with barrage tufas, paludal
environments with δ13C values of ca 10‰ indicative of C3 plants and fossil Hippopotamus, all of
which indicate a perennial water source. Other tufa deposits from Nyamita, Obware and Aringo
have a mixed C3/C4 signature consistent with a semi-arid C4 grassland surrounding these springfed
rivers. The δ18O values of tufa from Nyamita are on average ca 1‰ more negative than
calcite precipitated from modern rainfall in the region, suggesting greater contribution of
depleted monsoonal input, similar to the Last Glacial Maximum. Microdebitage and surface
collected artefacts indicate that early modern humans were utilizing these spring-fed rivers. The
presence of spring-fed rivers would have afforded animals a reliable water source, sustaining a
diverse plant and animal community in an otherwise arid environment.