Historians trace the first plague pandemic, which began with the Plague of the Byzantine emperor Justinian in 542, back to a disease reservoir in the remote Great Lakes region of Central Africa. Contemporary sources, however, spoke only of its coming from the Red Sea region. The idea that the Great Lakes plague reservoir was responsible for the ancient outbreak arose with the discovery of that reservoir by the bacteriologist Robert Koch in the 1890s and was further developed by biochemists in the mid-twentieth century and geneticists at the turn of the present century. More recent study of the plague bacterium suggests, however, that the African strain of Yersinia pestis arose only about five hundred years ago and is unrelated to the ancient strain responsible for the first pandemic. India was probably the source of both the plague of Justinian in the sixth century c.e. and the Great Lakes plague reservoir in the nineteenth century.