Captivated by the emerging research on mitochondrial DNA, in 1981 he joined Allan Wilson, a renowned biochemist at the Department of Biochemistry, University of California, Berkeley, under whose supervision he got a PhD in 1986.
His research was on human mtDNA variation, a follow-up of the work of Rebecca Cann, who was just completing her doctoral thesis from the same supervisor.
Then he worked as an Associate Research Scientist at the Department of Human Genetics, Cetus Corporation, Emeryville, California for a year.
He has been in the technical working group, DNA Analysis Methods of FBI between 1993 and 1998, Defense Science Board Task Force on DNA Technology for Identification of Ancient Remains (1994–1995), Wellcome Trust Bioarchaeology Panel (2001–2005), Steering Committee for National Energy Research Council (NERC) Program on Environmental Factors and the Chronology of Human Evolution and Dispersal (EFCHED) (2001–2006).
[4] In spite of criticisms, and religious antagonisms, even after two decades he still holds this view to be as valid as any scientific theory since a number independent research also corroborates their original human mtDNA phylogenetic tree.