The super-eruption of Toba, did it cause a human bottleneck?

Lake Toba, Sumatra, Indonesia, is the site of the largest volcanic explosion in the late Pleistocene, which occurred about 73,500 ( 2000) years ago (Chesner et al., 1991, Bühring & Sarnthein 2000). It has been asserted by Ambrose (1998) and others (Rampino & Self 1992, Rampino & Ambrose 2000, Rampino 2002) that the eruption gave rise to a “volcanic winter” of such a catastrophic scale that it caused a human population bottleneck. In this note we discuss the probable effect of the Toba eruption and the evidence that it caused the putative bottleneck. The super-eruption of Toba produced 2500– 3000 km of magma (dense rock equivalent) and probably injected at least 10 g of fine ash into the stratosphere (Rampino & Self 1993, Zielinski et al., 1996, Bühring & Sarnthein 2000). Pyroclastic flows covered about 10 km (Rampino & Self 1993) with lava reaching both the Malacca straits and the Indian Ocean (Rose & Chesner 1987). Layers of tephra, identified as Toba tuff have been found in India, more than 3000 km away from Toba (Ninkovich et al., 1978, Ninkovich 1979, Rose & Chesner 1987, Chesner et al., 1991, Pattan et al., 1999), and in the South China Sea (Bühring & Sarnthein 2000).