Diverse monsoon seasonality in eastern Africa recorded by papionin tooth enamel δ18O

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Green, Daniel R
Avila, Janaina N
Dirks, Wendy
Williams, Ian S
Smith, Tanya M
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2022
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Denver, USA

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Abstract

We report seasonal tooth enamel 618O profiles from six contemporaneous papionins spanning a gradient of aridity in eastern Africa from the Ethiopian rift (n = 5 teeth), to the Ethiopian high- lands (n = 2), to Ugandan forests (n = 2). Using the Sensitive High-Resolution Ion Microprobe (SHRIMP SI), serial samples from the innermost enamel demonstrate that these 17 years of c. weekly 618O measurements (n = 901) reflect the amounts and oxygen isotope composition of regional rainfall. Mean 618O values are highest in Papio hamadryas from the arid scrubland of the Awash rift (25.9 ‰, VSMOW), slightly lower in Theropithecus gelada from highlands near Derdre (24.8 ‰), and lowest in Papio anubis from mixed grassland and gallery forest near Rubirizi (21.6 ‰). 618O ranges are particularly useful in differentiating these hydrological regimes, with 618O values in highland papionins 2-3 ‰ lower than those in the rift. Lomb-Scargle frequency analysis of spatial 618O values transformed onto temporal scales using daily incremental features reveals dominant temporal 618O periods. Strong annual cycles are detected in all Ethiopian rift and highland teeth, but only weak cyclicity is found in Ugandan teeth, reflecting higher annual Ugandan rainfall with reduced seasonality. Particularly strong 6-month cycles are also detected in highland Theropithecus, a likely consequence of monsoon intensity and selective feeding by geladas on plants with 618O enrichment respon- sive to seasonal aridity. These data demonstrate that high resolution 618O data from primate enamel recover diverse monsoon and feeding patterns, aiding paleoenvironmental and behav- ioral reconstructions.

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American Journal of Biological Anthropology

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177

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S73

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ARC

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DP210101913

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Anthropology

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Life Sciences & Biomedicine

Evolutionary Biology

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Green, DR; Avila, JN; Dirks, W; Williams, IS; Smith, TM, Diverse monsoon seasonality in eastern Africa recorded by papionin tooth enamel δ18O, American Journal of Biological Anthropology, 2022, 177 (S73), pp. 72-72