Timing and causes of North African wet phases during the last glacial period and implications for modern human migration

Hoffmann, Dirk L.; Rogerson, Mike; Spötl, Christoph; Luetscher, Marc; Vance, Derek; Osborne, Anne H.; Fello, Nuri M.; Moseley, Gina E.

Abstract

We present the first speleothem-derived central North Africa rainfall record for the last glacial period. The record reveals three main wet periods at 65-61 ka, 52.5-50.5 ka and 37.5-33 ka that lead obliquity maxima and precession minima. We find additional minor wet episodes that are synchronous with Greenland interstadials. Our results demonstrate that sub-tropical hydrology is forced by both orbital cyclicity and North Atlantic moisture sources. The record shows that after the end of a Saharan wet phase around 70 ka ago, North Africa continued to intermittently receive substantially more rainfall than today, resulting in favourable environmental conditions for modern human expansion. The encounter and subsequent mixture of Neanderthals and modern humans – which, on genetic evidence, is considered to have occurred between 60 and 50 ka – occurred synchronously with the wet phase between 52.5 and 50.5 ka. Based on genetic evidence the dispersal of modern humans into Eurasia started less than 55 ka ago. This may have been initiated by dry conditions that prevailed in North Africa after 50.5 ka. The timing of a migration reversal of modern humans from Eurasia into North Africa is suggested to be coincident with the wet period between 37.5 and 33 ka.

Citation

Hoffmann, D. L., Rogerson, M., Spötl, C., Luetscher, M., Vance, D., Osborne, A. H., …Moseley, G. E. (2016). Timing and causes of North African wet phases during the last glacial period and implications for modern human migration. Scientific reports, 6(1), Article ARTN 36367. https://doi.org/10.1038/srep36367

• Acceptance Date: Sep 29, 2016
• Online Publication Date: Nov 3, 2016
• Publication Date: 2016-12
• Deposit Date: Jan 25, 2017
• Publicly Available Date: Jan 25, 2017
• Journal: Scientific reports
• Print ISSN: 2045-2322
• Electronic ISSN: 2045-2322
• Publisher: Nature Publishing Group
• Peer Reviewed: Not Peer Reviewed
• Volume: 6
• Issue: 1
• Article Number: ARTN 36367
• DOI: https://doi.org/10.1038/srep36367
• Keywords: Hydrology, Palaeoclimate
• Public URL: https://hull-repository.worktribe.com/output/447525
• Publisher URL: http://www.nature.com/articles/srep36367
• Additional Information: Copy of article: Hoffmann, D. L. et al. Timing and causes of North African wet phases during the last glacial period and implications for modern human migration. Sci. Rep. 6, 36367; doi: 10.1038/srep36367 (2016).