Axel Timmermann - Climate-induced migration of early Homo Sapiens

Event type: 
16 May 2018
2.00 - 3.00pm

Climate Change Research Centre, Seminar Room, Mathews Building 4th floor, UNSW, Sydney

Axel Timmermann
IBS Center for Climate Physics, Pusan National University
Climate Change Research Centre, UNSW, Australia

Our climate system varies on a wide range of timescales, from seasons to several millions of years. A large part of this variability is internally generated as a result of instabilities of the coupled atmosphere-ocean-ice-carbon cycle system. Other modes of variability, such as glacial cycles, are caused by astronomical forcings with periods of 20, 40, 100 thousand years. These so-called Milankovitch Cycles are associated with earths axis wobble, axis obliquity and shifts in the eccentricity of earths orbit around the sun, respectively. When these cycles conspire, they can cause the climate system to plunge into an ice-age. This happened last time 110,000 years ago, when Northern Hemisphere summer radiation decreased substantially, and ice-sheets started to form as a result. Around 100,000 years ago northern Hemisphere summer moved again closer to the sun and Homo sapiens started to leave Africa across vegetated corridors in Northeastern Africa and the Arabian Peninsula. This first migration wave must have been relatively weak, but it left unequivocal traces in the fossil and archaeological record. Why Homo sapiens embarked on its grand journey across our planet during glacial climate conditions has been subject of an intense debate in various scientific communities. Moreover, the archaeological records of an early exodus around 100 thousand years ago seem to be at odds with paleo-genetic evidences, that place the first dispersal out of Africa around 70-60 thousand years ago.

To elucidate what role climate and environmental conditions played in the dispersal of Anatomically Modern Humans out of Africa, we have developed and applied one of the first integrated climate/human migration computer models. The model simulates ice-ages, abrupt climate change, the peoplingof our planet and captures the arrival time of Homo sapiens in the Levant, Arabian Peninsula, Southern China and Australia in close agreement with paleo climate reconstructions, fossil and archaeological evidence.

The human dispersal model simulates multiple prominent migration waves of Homo sapiens across the Arabian Peninsula and the Levant region around 106-94, 89-73, 59-47 and 45-29 thousand years ago. These waves were caused by earths axis wobble and its corresponding changes in climate seasonality and resulting large-scale shifts in vegetation in tropical/subtropical regions. Such shifts opened up green corridors between Africa, the Sinai and the Arabian Peninsula, enabling Homo sapiens to leave Northeastern Africa and migrate into Asia, Europe, Australia and eventually into the Americas. The model also simulates a complex pattern of human dispersal out of Africa and back flow into Africa, that challenges the more unidirectional away-from-Africa perspective that is still very prevalent in anthropology and some genetic studies.

Paleo-genetic reconstructions indicate that the first exodus out of Africa must have occurred around 70-60 thousand years ago. In contrast, our computer simulations and paleo-climate data show that northeastern Africa experienced one of its most severe long-term droughts during this time. The resulting large desert areas would have been an impenetrable natural border for early human migration.

More research needs to be done to help reconcile and synthesize genetic, archaeological, climatological and anthropological data.


Speaker Biography: Axel Timmermann conducted his PhD research at the Max Planck Institute of Meteorology in Hamburg, Germany and received his PhD in Meteorology in 1999 from the University of Hamburg. After 2 years as a postdoc in the Netherlands and 3 years as research team leader at the IfM-GEOMAR/University of Kiel, Germany he moved to the University of Hawaii to work first as an associate professor and then from 2009- 2016 as a full tenured professor at the International Pacific Research Center and the Department of Oceanography. In January 2017 Dr. Timmermann became the Director of the new IBS Center for Climate Physics (ICCP) at Pusan National University, where he also holds a Distinguished Professorship.

In 2008 Axel Timmermann received the prestigious Rosenstiel Award in Oceanographic Science for his fundamental contributions to ocean science. In 2015 he was awarded the University of Hawaii RegentsMedal for Research Excellence and in the same year he also became a Fellow of the American Geophysical Union. In April 2017 Prof. Timmermann received the Milankovic Medal from the European Geosciences Union in 2017 for his contributions to paleoclimate research. He has published over 150 peer-reviewed articles on subjects ranging from Quark-Gluon Plasma, relativistic hydrodynamics, the El Niño-Southern Oscillation, glacial cycles, abrupt climate change, climate prediction, human migration, bio-optics and dynamical systemstheory.