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An ecometric analysis of the fossil mammal record of the Turkana Basin

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ABSTRACT

Although ecometric methods have been used to analyse fossil mammal faunas and environments of Eurasia and North America, such methods have not yet been applied to the rich fossil mammal record of eastern Africa. Here we report results from analysis of a combined dataset spanning east and west Turkana from Kenya between 7 and 1 million years ago (Ma). We provide temporally and spatially resolved estimates of temperature and precipitation and discuss their relationship to patterns of faunal change, and propose a new hypothesis to explain the lack of a temperature trend. We suggest that the regionally arid Turkana Basin may between 4 and 2 Ma have acted as a ‘species factory’, generating ecological adaptations in advance of the global trend. We show a persistent difference between the eastern and western sides of the Turkana Basin and suggest that the wetlands of the shallow eastern side could have provided additional humidity to the terrestrial ecosystems. Pending further research, a transient episode of faunal change centred at the time of the KBS Member (1.87–1.53 Ma), may be equally plausibly attributed to climate change or to a top-down ecological cascade initiated by the entry of technologically sophisticated humans.

This article is part of the themed issue ‘Major transitions in human evolution’.

No MeSH data available.


Estimates of mean annual precipitation (mm/yr) over time in the Turkana basin using two different levels of aggregation (right–left) and two different models based on the dental ecometrics HYP and LOP (up–down). 95% CIs for the fit are shown in orange.
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RSTB20150232F4: Estimates of mean annual precipitation (mm/yr) over time in the Turkana basin using two different levels of aggregation (right–left) and two different models based on the dental ecometrics HYP and LOP (up–down). 95% CIs for the fit are shown in orange.

Mentions: As expected from previous studies, humidity in the Turkana Basin declined from the late Miocene, reaching a lower plateau during the Plio-Pleistocene (figure 4). Depending on the model used, the decline was gradual during the Pliocene or quite abrupt soon after the still-humid time around 4 Ma. In addition, there may be one or two intervals of increased variance. All models show a great spread of values near 1.8 Ma, but only some also show this near 3.5 Ma. It is presently not possible to tell from data or analytical results whether this increased variability indicates increased sampling density, increased spatial heterogeneity or increased temporal variation. However, the fact that such periods of increased variance are not seen for the temperature estimates suggests that something beyond sampling is involved.Figure 4.


An ecometric analysis of the fossil mammal record of the Turkana Basin
Estimates of mean annual precipitation (mm/yr) over time in the Turkana basin using two different levels of aggregation (right–left) and two different models based on the dental ecometrics HYP and LOP (up–down). 95% CIs for the fit are shown in orange.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4920289&req=5

RSTB20150232F4: Estimates of mean annual precipitation (mm/yr) over time in the Turkana basin using two different levels of aggregation (right–left) and two different models based on the dental ecometrics HYP and LOP (up–down). 95% CIs for the fit are shown in orange.
Mentions: As expected from previous studies, humidity in the Turkana Basin declined from the late Miocene, reaching a lower plateau during the Plio-Pleistocene (figure 4). Depending on the model used, the decline was gradual during the Pliocene or quite abrupt soon after the still-humid time around 4 Ma. In addition, there may be one or two intervals of increased variance. All models show a great spread of values near 1.8 Ma, but only some also show this near 3.5 Ma. It is presently not possible to tell from data or analytical results whether this increased variability indicates increased sampling density, increased spatial heterogeneity or increased temporal variation. However, the fact that such periods of increased variance are not seen for the temperature estimates suggests that something beyond sampling is involved.Figure 4.

View Article: PubMed Central - PubMed

ABSTRACT

Although ecometric methods have been used to analyse fossil mammal faunas and environments of Eurasia and North America, such methods have not yet been applied to the rich fossil mammal record of eastern Africa. Here we report results from analysis of a combined dataset spanning east and west Turkana from Kenya between 7 and 1 million years ago (Ma). We provide temporally and spatially resolved estimates of temperature and precipitation and discuss their relationship to patterns of faunal change, and propose a new hypothesis to explain the lack of a temperature trend. We suggest that the regionally arid Turkana Basin may between 4 and 2 Ma have acted as a ‘species factory’, generating ecological adaptations in advance of the global trend. We show a persistent difference between the eastern and western sides of the Turkana Basin and suggest that the wetlands of the shallow eastern side could have provided additional humidity to the terrestrial ecosystems. Pending further research, a transient episode of faunal change centred at the time of the KBS Member (1.87–1.53 Ma), may be equally plausibly attributed to climate change or to a top-down ecological cascade initiated by the entry of technologically sophisticated humans.

This article is part of the themed issue ‘Major transitions in human evolution’.

No MeSH data available.