Humanity’s shadow: The spread of man across the Earth

It all started with a woman. Or at least, we can trace it back to one. The origin of the species Homo sapiens, a likely descendant of Homo erectus can be linked to the DNA of a single female specimen scientists called ‘Eve.’

Now before everyone starts preparing for the rapture we must be clear that Eve was not our earliest ancestor, nor was she the first woman. Rather, she was an early modern human from a time when modern humans were rather rare. The important thing to note is: Eve, and everyone else at that time, originated in Africa.

Figure 1: Homo erectus

Figure 2: Homo sapiens

The date for the advent of Homo sapiens is around 200 000 years ago. Prior to this, Homo erectus, the first hominid to tame fire, is thought to have migrated from Africa to Arabia, Asia and Europe some 800 000 years ago. Homo sapiens soon outstripped its predecessor however, moving out of Africa around 125 000 years ago. Between 85000-75000 years ago, humans spread from Arabia to India, Borneo and South China, hugging the coast all the while. By 60 000 years ago, Australia was no longer virgin territory, humans having crossed there from South-east Asia. Finally, a changing climate 50 000 years ago was the catalyst which allowed humans to migrate up into Europe. Central and North-east Asia were next for our intrepid ancestors, and the colonisation of Siberia around 40 000 years ago preceded expansion into the Americas.

The colonisation of the New World was remarkable in that the spread of humans was so rapid. Indeed, we could say it was plague-y. Human predation is listed as a primary reason for the disappearance of 35 genera of large mammals including ground sloths, giant tapirs, large predators and mammoths. Plague or not, humanity managed to expand over the course of only 10 000 years from North America down into South America. There is evidence that the expansion to the Americas may even have involved watercraft, with humans expanding along the coast then into the interior of these continents. Regardless of how it was achieved, by 12500 years ago, our distribution was almost global. An excellent interactive map of this human migration is available here.

Figure 3: The now extinct Giant Ground Sloth

In a relatively short time (in evolutionary terms), humans learnt to co-operate, to live in communities, communicate ideas and even to sail. We colonised islands and icy places, increasingly using our technology and great ingenuity to shape the world to our own ideal.

References

BROWN, J.H. & LOMOLINO, M.V.1998. Biogeography. 2^nd Edition. Sinauer Associates Inc., Massachusetts.

GUGLIOTTA, G. 2008. The Great Human Migration. http://www.smithsonianmag.com/history-archaeology/human-migration.html?c=y&page=5 (Accessed 25/04/2013).

GRAYSON, D.K. 2001. The Archaeological Record of Human Impacts on Animal Populations. Journal of World Prehistory 15(1): 1-68.