Out of Africa: new hypotheses and evidence for the dispersal of Homo sapiens along the Indian Ocean rim

Abstract

The dispersal of Homo sapiens out of Africa is a significant topic in human evolutionary studies. Most investigators agree that our species arose in Africa and subsequently spread out to occupy much of Eurasia. Researchers have argued that populations expanded along the Indian Ocean rim at ca 60 000 years ago during a single rapid dispersal event, probably employing a coastal route towards Australasia. Archaeologists have been relatively silent about the movement and expansion of human populations in terrestrial environments along the Indian Ocean rim, although it is clear that Homo sapiens reached Australia by ca 45 000 years ago. Here, we synthesize and document current genetic and archaeological evidence from two major landmasses, the Arabian peninsula and the Indian subcontinent, regions that have been underplayed in the story of out of Africa dispersals. We suggest that modern humans were present in Arabia and South Asia earlier than currently believed, and probably coincident with the presence of Homo sapiens in the Levant between ca 130 and 70 000 years ago. We show that climatic and environmental fluctuations during the Late Pleistocene would have had significant demographic effects on Arabian and South Asian populations, though indigenous populations would have responded in different ways. Based on a review of the current genetic, archaeological and environmental data, we indicate that demographic patterns in Arabia and South Asia are more interesting and complex than surmised to date.

Keywords::

• Dispersals
• Homo sapiens
• Indian Ocean
• Arabia
• South Asia

Acknowledgements

Petraglia appreciates the invitation of the Society for the Study of Human Biology to present a version of this paper at the Human Dispersals symposium at the University of Rome. The Saudi Commission for Antiquities and Museums is thanked for granting permission to conduct research in the Kingdom. The Archaeological Survey of India granted permits to conduct field work in India. The American Institute of American Studies provided administrative support for conducting our research. Abdullah Alsharekh, Remy Crassard, Ravi Korisettar and Jeff Rose are thanked for recent discussions about the Arabian and South Asian record. We thank two anonymous reviewers for helpful comments on a draft of this article.

Declaration of interest: The British Academy and the Leverhulme Trust provided major funding for our field studies. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.