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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.


Comparison of mean annual precipitation (mm/yr) between localities from the east and west sides of present-day lake Turkana over time, with the same models and fit as in figures 3 and 4.
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RSTB20150232F6: Comparison of mean annual precipitation (mm/yr) between localities from the east and west sides of present-day lake Turkana over time, with the same models and fit as in figures 3 and 4.

Mentions: Comparing the temporal trends of the two sides of the basin reveals a clear difference over time (figure 6), regardless of resolution (mode of aggregation). The wetter east side has a greater spread of values, possibly reflecting better sampling but perhaps also suggesting greater spatial heterogeneity or greater sensitivity to fluctuations in the water table, related to influx of river water rather than rainfall. Under such an interpretation, the elevation of the estimates from the east side would be due to local surface or ground water and, potentially, teleconnection to climatic changes elsewhere, rather than to greater local rainfall on the east side. This interpretation appears climatologically more plausible and is supported by some of the most humid ComLocs being situated in areas where sedimentology records the presence of river mouths and palaeodeltas [44,48].Figure 6.


An ecometric analysis of the fossil mammal record of the Turkana Basin
Comparison of mean annual precipitation (mm/yr) between localities from the east and west sides of present-day lake Turkana over time, with the same models and fit as in figures 3 and 4.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

RSTB20150232F6: Comparison of mean annual precipitation (mm/yr) between localities from the east and west sides of present-day lake Turkana over time, with the same models and fit as in figures 3 and 4.
Mentions: Comparing the temporal trends of the two sides of the basin reveals a clear difference over time (figure 6), regardless of resolution (mode of aggregation). The wetter east side has a greater spread of values, possibly reflecting better sampling but perhaps also suggesting greater spatial heterogeneity or greater sensitivity to fluctuations in the water table, related to influx of river water rather than rainfall. Under such an interpretation, the elevation of the estimates from the east side would be due to local surface or ground water and, potentially, teleconnection to climatic changes elsewhere, rather than to greater local rainfall on the east side. This interpretation appears climatologically more plausible and is supported by some of the most humid ComLocs being situated in areas where sedimentology records the presence of river mouths and palaeodeltas [44,48].Figure 6.

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.