DID CLIMATE DRIVE FAUNAL SUCCESSION AND HOMININ CULTURAL CHANGE IN EAST AFRICA BETWEEN 300 AND 500 KA?

Did East African climate impact the evolution of our species? A focus in recent years has been on climate variability and the inherent stress it places on environmental predictability and survival. The amplitude of change in sea surface and bottom water temperatures, of marine foram δ¹⁸O, and of African dust accumulation in surrounding oceans all indicate that climate variability has intensified on the African landscape over the past 5 million years. A major shift in early hominin behavior and mammalian community structure occurred in East Africa some time between 500 and 300 ka (Brooks et al., 2018; Potts et al., 2018). This interval marks the transition from Acheulean hand axe technology to the early Middle Stone Age, and an impressive turnover in large mammalian fauna as well. With this in mind, we have undertaken analyses of biomarkers for past temperature in the Lake Malawi drill core (11º S, 34º E) in the 300 – 500 ka interval, with temporal resolution of ~1 ky. We found branched glycerol dialkyl glycerol tetraethers (brGDGTs) to be as abundant as isoprenoid GDGTs in this portion of the sedimentary record, and provided the more reliable temperature history. Thus far we have a brGDGT temperature record that extends roughly from 320 to 470 ka, which displays a strong glacial/interglacial cycle with lake water temperature ranging between 21º and 29ºC – most likely a greater range than the overlying air temperature would have experienced. What is particularly apparent is how abruptly warming happened during glacial Termination 5. We propose that this played a significant role in driving the dramatic changes in mammal communities and human culture that happened around this time. More analyses are underway, including for δ¹³C and δ²H of leaf wax n-alkanes to resolve the hydrological change that accompanied the temperature history in the region.

Brooks, A. S. et al., 2018, Science, v. 360, p. 90-94.

Potts, Ret al.., 2018, Science, v. 360, p. 86-90.