Rapid climate variability has been hypothesized to play an important role in hominin evolution, yet our knowledge of Plio-Pleistocene climate change on short timescales is poor. Here, we developed centennial-scale reconstructions of precipitation from leaf wax biomarker hydrogen isotope ratios (δDwax) using lacustrine sediment from West Turkana, Kenya. We analyzed two time intervals (∼1.72 and ∼1.60 Ma) with different orbital configurations (0.043 and 0.025 eccentricity, respectively) to examine the influence of seasonal insolation forcing on high-frequency climate variability and the rates of climate transitions. Our data indicate that under low summer insolation, which should induce high latitude glaciation and tropical African aridity, millennial-scale climate variability was stronger. This suggests that hominins may have been forced to contend with increased climate variability during already extreme environmental conditions. Additionally, we observe a rapid shift from arid to humid conditions occurring in less than 200 years under high-amplitude precessional-scale insolation change. The rate of this transition is similar to that observed in some proxy records of the onset of the African Humid Period, indicating high sensitivity to gradual insolation forcing in the Turkana Basin. Such abrupt climate changes could induce evolutionary selection for generalist behavioral traits in hominins.
Bibliographical noteFunding Information:
We wish to thank Marcelo Alexandre and Ewerton Santos for laboratory assistance, Rick Potts for suggestions on an earlier draft of the manuscript, and the members of the Hominin Sites and Paleolakes Drilling Project for useful discussions. Initial core processing and sampling were conducted at the US National Lacustrine Core Facility (LacCore) at the University of Minnesota. Thanks to the Kenyan National Council for Science and Technology and the Kenyan Ministry of Mines for research and export permits; the National Environmental Management Authority of Kenya for environmental drilling permits; DOSECC Exploration Services; Drilling and Prospecting International Ltd; the Nariokotome Mission and the people of Nariokotome. We would also like to thank Boniface Kimeu and Francis Ekai, and the members of the West Turkana science field team: Chris Campisano, Chad Yost, Sarah Ivory, Les Dullo, Tannis McCartney, Ryan O’Grady, Gladys Tuitoek, Elizabeth Kimburi, and Thomas Johnson. This research was partially supported by National Science Foundation (NSF) grants EAR 1123942 , EAR 1338553 , EAR 1826938 , and BCS 1241859 , by the International Continental Scientific Drilling Program (ICDP), and by grants from the Institute at Brown for Environment and Society (IBES) and the Geological Society of America (GSA) (to R.L.L.). Data are available at the World Data Center-A for Paleoclimatology. We thank anonymous reviewers for helpful comments on an earlier version of this manuscript. This is publication # of the HSPDP.
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- East africa
- Human evolution
- Organic geochemistry
- Stable isotopes
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