Toba catastrophe theory (http://en.wikipedia.org/wiki/Toba_catastrophe_theory)
Late Pleistocene human population bottlenecks, volcanic winter, and differentiation of modern humans (http://ice2.uab.cat/argo/Argo_actualitzacio/argo_butlleti/ccee/geologia/arxius/1Ambrose%201998.pdf)-----Extract (http://www.bradshawfoundation.com/stanley_ambrose.php)