Climate stage· The columns of time
MIS 9
337 ka → 300 ka
A warm stage, and the one in which the oldest fossils of our species are usually placed. If the species has a climatic setting at its origin, this is it.
What the evidence shows
Odd numbers mark interglacials, and MIS 9 is among the warmer of the last half million years. What warmth does to Africa is the part that matters here. A compilation of continental and marine records identifies more than 230 green Sahara periods in the last eight million years, each taking two to three millennia to develop, peaking over four to eight, and ending as quickly as it began. During such a period the desert carries savannah and connects the African tropics to the mid latitudes of Africa and Eurasia, and the dated succession of these episodes lines up with the ages of Saharan archaeological and hominin sites.
Bounds and conventions
Two datings meet here and neither is precise enough to constrain the other. The stage boundaries come from a smoothed global curve; the Jebel Irhoud age carries 34,000 years of error, wide enough to touch the neighbouring stages. Saying our species appears during MIS 9 is defensible; saying it appears because of MIS 9 is not.
An interglacial.
Sources
- Lisiecki, L. E., Raymo, M. E. (2005). A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records. Paleoceanography 20, PA1003.
- Richter, D., Grün, R., Joannes-Boyau, R., et al. (2017). The age of the hominin fossils from Jebel Irhoud, Morocco, and the origins of the Middle Stone Age. Nature 546, 293–296.
- Larrasoaña, J. C., Roberts, A. P., Rohling, E. J. (2013). Dynamics of Green Sahara Periods and Their Role in Hominin Evolution. PLoS ONE 8(10), e76514.