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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.


Relationship of species detected to specimens collected in the analysed dataset, showing exceptionally high species/specimen ratio of the KBS Member. The fit is by cubic smoothing spline with 4 degrees of freedom.
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RSTB20150232F7: Relationship of species detected to specimens collected in the analysed dataset, showing exceptionally high species/specimen ratio of the KBS Member. The fit is by cubic smoothing spline with 4 degrees of freedom.

Mentions: The ratio of specimens collected to taxa identified is quite stable in the data but one anomaly stands out: the extremely well-sampled KBS Member at Koobi Fora (1.87–1.53 Ma) has a much lower ratio of specimens to species than do other intervals (figure 7). This includes the preceding and equally well-sampled Upper Burgi Member (2.00–1.87 Ma), suggesting that sampling intensity alone is not the cause. This anomaly corresponds to a major turnover event described below but apart from the possible increase in temporal or spatial variability, there is no indication of a corresponding major local climate effect in the ecometrics (figure 6).Figure 7.


An ecometric analysis of the fossil mammal record of the Turkana Basin
Relationship of species detected to specimens collected in the analysed dataset, showing exceptionally high species/specimen ratio of the KBS Member. The fit is by cubic smoothing spline with 4 degrees of freedom.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

RSTB20150232F7: Relationship of species detected to specimens collected in the analysed dataset, showing exceptionally high species/specimen ratio of the KBS Member. The fit is by cubic smoothing spline with 4 degrees of freedom.
Mentions: The ratio of specimens collected to taxa identified is quite stable in the data but one anomaly stands out: the extremely well-sampled KBS Member at Koobi Fora (1.87–1.53 Ma) has a much lower ratio of specimens to species than do other intervals (figure 7). This includes the preceding and equally well-sampled Upper Burgi Member (2.00–1.87 Ma), suggesting that sampling intensity alone is not the cause. This anomaly corresponds to a major turnover event described below but apart from the possible increase in temporal or spatial variability, there is no indication of a corresponding major local climate effect in the ecometrics (figure 6).Figure 7.

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.