Was humankind's first exit from Africa a failed activity?

Was humankind's first exit from Africa a failed activity?

Prior posts have noted that the accepted wisdom is that some humans left Africa about 60 thousand years ago, and thereafter migrated all over the world. 

Now, researchers have found stone tools at a site in the Arabian Peninsula that suggests movement some 125 thousand years ago.  Many advocates for a later (more recent) exit argue that the eruption of Indonesia's Mount Toba around 74 thousand years ago created a "volcanic winter" that decimated modern human populations in Africa and rendered the Indian subcontinent uninhabitable for thousands of years.  Advocates for an earlier exit contend that the eruption was relatively minor and the climatic effect short-lived.

While archeologists agree that the new dating supports an "early push" into Arabia, the agreement ends there.  Supporters point to discoveries that suggest humans made it to parts of India before the Mt. Toba blast, and in fact survived the blast.  Opponents argue that many such migrations were dead-end.  They point to caves in Israeli sites at which human occupation apparently occurred about 100 thousand years ago, but were replaced by Neandertals by 70 thousand years ago.  Paleobiologists also argue that the Mt. Toba exposion set off 10 thousand years of extreme cold and environmental devastation, pointing to (among other things) pollen evidence.  Did we survive, or not?

Archeologist would like to explore areas of Iran for further evidence to this question, but the current political climate renders that unlikely to occur.  Expect the debate to continue.

The report on the new findings in Arabia can be found at http://www.sciencemag.org/content/331/6016/453.abstract.  See also http://www.sciencedaily.com/releases/2011/01/110127141651.htm.