Climate is thought to play a critical role in human evolution; however, this hypothesis is difficult to test due to a lack of long, high-quality paleoclimate records from key hominin fossil locales. To address this issue, we analyzed organic geochemical indicators of climate in a drill core from West Turkana, Kenya that spans ∼1.9–1.4 Ma, an interval that includes several important hominin evolutionary transitions. We analyzed the hydrogen isotopic composition of terrestrial plant waxes (δDwax) to reconstruct orbital-timescale changes in regional hydrology and their relationship with global climate forcings and the hominin fossil record. Our data indicate little change in the long-term mean hydroclimate during this interval, in contrast to inferred changes in the level of Lake Turkana, suggesting that lake level may be responding dominantly to deltaic progradation or tectonically-driven changes in basin configuration as opposed to hydroclimate. Time-series spectral analyses of the isotopic data reveal strong precession-band (21 kyr) periodicity, indicating that regional hydroclimate was strongly affected by changes in insolation. We observe an interval of particularly high-amplitude hydrologic variation at ∼1.7 Ma, which occurs during a time of high orbital eccentricity hence large changes in processionally-driven insolation amplitude. This interval overlaps with multiple hominin species turnovers, the appearance of new stone tool technology, and hominin dispersal out of Africa, supporting the notion that climate variability played an important role in hominin evolution.
Bibliographical noteFunding Information:
We wish to thank Laura Messier for sample preparation, Rafael Tarozo for laboratory assistance, Sylvia Dee and Martin Trauth for assistance with statistical analyses, 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. Support for HSPDP has been provided by the National Science Foundation (NSF) grants EAR 1123942 , EAR 1338553 , and BCS 1241859 , the International Continental Scientific Drilling Program (ICDP) , and the Institute at Brown for Environment and Society, Brown University (IBES) . Data are freely available at the World Data Center-A for Paleoclimatology. We thank Kevin Uno and an anonymous reviewer for helpful comments on an earlier version of this manuscript. This is publication 11 of the Hominin Sites and Paleolakes Drilling Project. Appendix A
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- Continental biomarkers
- East Africa
- Human evolution
- Hydrogen isotopes
- Organic geochemistry
- Turkana basin