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

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.


Related in: MedlinePlus

Distribution of ecometric mean annual precipitation (regression model) from ComLocs in the Turkana Basin during four time intervals. The apparent precipitation minimum in the 3–2 Ma interval is partly owing to extremely low estimates from the Kalochoro Member of West Turkana. GIS settings: inverse distance weighting with distance coefficient 2.0, radius 1: 0.2, radius 2: 0.2, resize width: 1000, resize height: 1000.
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RSTB20150232F5: Distribution of ecometric mean annual precipitation (regression model) from ComLocs in the Turkana Basin during four time intervals. The apparent precipitation minimum in the 3–2 Ma interval is partly owing to extremely low estimates from the Kalochoro Member of West Turkana. GIS settings: inverse distance weighting with distance coefficient 2.0, radius 1: 0.2, radius 2: 0.2, resize width: 1000, resize height: 1000.

Mentions: Ecometric precipitation maps for Turkana show the spatial details of the temporal trends (figure 5). The emergence of an east-west contrast is seen from 4 Ma onwards, as soon as the present tectonic structure was created [44]. The shallow eastern side of the half-graben appears more humid than the elevated western side and, especially after 2 Ma, more spatially heterogeneous, in agreement with previous work [11,45]. The hypothesis that temporal variability also increased regionally as a result of orbital forcing [46,47] is entirely consistent with our results but cannot be independently supported, owing to the low temporal resolution available to us.Figure 5.


An ecometric analysis of the fossil mammal record of the Turkana Basin
Distribution of ecometric mean annual precipitation (regression model) from ComLocs in the Turkana Basin during four time intervals. The apparent precipitation minimum in the 3–2 Ma interval is partly owing to extremely low estimates from the Kalochoro Member of West Turkana. GIS settings: inverse distance weighting with distance coefficient 2.0, radius 1: 0.2, radius 2: 0.2, resize width: 1000, resize height: 1000.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

RSTB20150232F5: Distribution of ecometric mean annual precipitation (regression model) from ComLocs in the Turkana Basin during four time intervals. The apparent precipitation minimum in the 3–2 Ma interval is partly owing to extremely low estimates from the Kalochoro Member of West Turkana. GIS settings: inverse distance weighting with distance coefficient 2.0, radius 1: 0.2, radius 2: 0.2, resize width: 1000, resize height: 1000.
Mentions: Ecometric precipitation maps for Turkana show the spatial details of the temporal trends (figure 5). The emergence of an east-west contrast is seen from 4 Ma onwards, as soon as the present tectonic structure was created [44]. The shallow eastern side of the half-graben appears more humid than the elevated western side and, especially after 2 Ma, more spatially heterogeneous, in agreement with previous work [11,45]. The hypothesis that temporal variability also increased regionally as a result of orbital forcing [46,47] is entirely consistent with our results but cannot be independently supported, owing to the low temporal resolution available to us.Figure 5.

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.


Related in: MedlinePlus