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Humans may have come close to extinction about 70,000 years ago, according to the latest genetic research....The study suggests that at one point there may have been only 2,000 individuals alive as our species teetered on the brink.

The actual number was 8 and it happened a lot more recently than that.

I thought Toba might be responsible too, but the more I think about it the less sense it makes. How come Toba did not restrict the genes of Chimps or anything else, just humans?

It is clear that Man is a very recent arrival, how recent is up for debate. They gave a 70-140K window, but that is based on a lot of assumptions about population size. It is also based on the idea that mutation rates have remained constant.

That is not a reliable assumption when you consider that the Vela Supernova bathed Earth in radiation at several times its current rate for thousands of years. That would mean the mutation rate in the past was higher than the current rate they are using to make those calculations. That might move the DNA appearance of man to the cultural appearance of man (40K).