Terry, your guess looks pretty good. From that same H. Ergaster link:

"By 1.6 million years ago, an advance in stone tool technology is identified with H. ergaster. Known as the Achulean stone tool industry, it consisted of large cutting tools, primarily hand axes and cleavers. Originally thought to be responsible for the spread of early humans beyond Africa, it is now known that the migration out of Africa predates this tool industry."

Maybe I'm missing something important, but this seems to be making a mockery of the significance of migrations 70,000-40,000 yrs ago.

"Time is what prevents everything from happening at once" - John Wheeler