Out of Africa 2 - Homo sapien dispersal - a review

We've now learnt that all human beings today can trace their origin back to Africa, so now I bet you're wondering about how this second Out of Africa dispersal played out.

Today we have wind back 200,000 years ago (ya), our location is East Africa. Over a million years have past since Homo erectus successfully migrated, and they have now set up home throughout Asia and Europe. The earliest known remains of H. sapien are found in Ethiopia 160,000ya. From this singular east African origin, three lines diverged, one travelling to southern Africa, one to Central and West Africa, and the last line traveled North. It is this last lineage we are interested as this small group are the ancestors of every non African person in the World. 

Figure 1 The range of other Hominid groups and our dispersal route.
1 = H. sapien
2 = Neanderthal
3 = H. erectus

The most widely supported route these early H. sapiens took is strikingly similar to the H. erectus dispersal I described in Out of Africa 1 - Homo erectus dispersal - climate induced changes in sea level enabled a crossing of the red sea and into the Arabian peninsular.  Ericksson's 2011 paper lends support to the importance of climate in facilitating the migration, he explains that '60-70kya (thousand years ago) the global colonisation of humans ancestral to modern populations was prevented by the arid climate in Northern Africa and much of the Arabian peninsular.' Long after spreading throughout Asia they traveled North into Europe, following game migrations and favorable climates. 

Upon reaching the China region 70,000ya there was a divergence. It seems one group island hopped through Indonesia, eventually entering Australia 50,000ya; whilst another group dispersed Northwards, crossing into the Americas 15,000ya. 

An opposing view is presented in  Rasmussen et al.  2011 paper. They used DNA analysis of an aborigine’s lock of hair and discovered a greater similarity to African DNA compared to Asian and European. These findings go against the idea that a single migration occurred and that the Australian population diverged from the Asian one. Instead it suggests that the ancestors of the Australian population left Africa first 75,000ya, travelling along the South Asian coast and interbreeding with the Denisovian population before arriving in Australia. The evidence of these travels would then have been swallowed up by rising sea levels; the Asian and Europeans would then have emerged from Africa separately at a later date around 25,000-38-000ya. The main archaeological evidence to back up this theory comes from the 'Mungo man'a 50,000ya skeleton found in Australia. the path this early migration may have taken has not preserved and so there is minimal physical evidence however new technique of matching DNA to powerful computer models is reputed to make up for this; however the research is still very new and it will be interesting to see if it stands up to academic scrutiny over the coming years. 

Alternative dispersal routes