The Toba eruption could very well have driven humans south in to Australia.. ( 6 year "nuclear" winter, subsequent 1000 year ice age provides adequate ice-overs in the southern hemisphere for desperate humans to attempt escaping disaster )
It may be found that the first migrations were even earlier than presently thought..
Some human activity/artifacts have been found in Indonesia that date to shortly after Toba exploded. No-one knows if they survived the 'winter' caused by Toba...they apparently did survive the explosion for some time afterward.