Philip Dei
Wed, Jul-23-03, 06:12
Influence of Plio-Pleistocene aridification on human
evolution: Evidence from paleosols of the Turkana Basin,
Kenya. Jonathan Guy Wynn
Abstract New stable carbon isotope measurements, coupled with
paleoprecipitation estimates, both from Plio-Pleistocene
paleosols of the Turkana Basin, Kenya, provide a
high-resolution record of aridification and increasing C4
biomass during the past 4.3 Ma. This aridification trend is
marked by several punctuations at 3.58-3.35, 2.52-2, and
1.81-1.58 Ma, during which the running mean and variance of
13C and paleoaridity estimates increase, suggesting that the
proportion of C4 biomass increases in savanna mosaics during
periods of heightened aridity. Increase in C4 biomass during
these aridification events not only increases the proportion
of open habitats, but increases the spatial neg-entropy, or
heterogeneity of the ecosystem. The aridification events
identified correspond to intervals of increased turnover,
but more importantly, increased diversity of bovids.
Although the record of hominins from the Turkana Basin lacks
the temporal resolution and diversity of the bovid record,
the aridification intervals identified are marked by similar
increases in the diversity and turnover of hominins. These
results support the hypothesis that hominins evolved in
savanna mosaics that changed through time, and suggest that
the evolution of bovids and hominins was driven by shifts in
climatic instability and habitat variability, both
diachronic and synchronic.
evolution: Evidence from paleosols of the Turkana Basin,
Kenya. Jonathan Guy Wynn
Abstract New stable carbon isotope measurements, coupled with
paleoprecipitation estimates, both from Plio-Pleistocene
paleosols of the Turkana Basin, Kenya, provide a
high-resolution record of aridification and increasing C4
biomass during the past 4.3 Ma. This aridification trend is
marked by several punctuations at 3.58-3.35, 2.52-2, and
1.81-1.58 Ma, during which the running mean and variance of
13C and paleoaridity estimates increase, suggesting that the
proportion of C4 biomass increases in savanna mosaics during
periods of heightened aridity. Increase in C4 biomass during
these aridification events not only increases the proportion
of open habitats, but increases the spatial neg-entropy, or
heterogeneity of the ecosystem. The aridification events
identified correspond to intervals of increased turnover,
but more importantly, increased diversity of bovids.
Although the record of hominins from the Turkana Basin lacks
the temporal resolution and diversity of the bovid record,
the aridification intervals identified are marked by similar
increases in the diversity and turnover of hominins. These
results support the hypothesis that hominins evolved in
savanna mosaics that changed through time, and suggest that
the evolution of bovids and hominins was driven by shifts in
climatic instability and habitat variability, both
diachronic and synchronic.