Jane...interesting point. I learn a lot of my general science on TV, and a show did link the Toba volcanic eruption to the population bottleneck (that previously was published as us all descending from one woman ("Eve", of course) by study of mitocondrial (sp??) DNA about 100,000 years ago. What I don't know, and you correctly point out that the AGU abstract does not say, is whether the drought in Africa has been linked to the eruption. Scholz may know this, as the Toba eruption is widely-known by geologists, but just did not say it in his abstract. If no one has published this link, someone could...

I guess one question is whether both the drought and the Toba eruption are well-enough dated to know that the Toba eruption immediately preceded the drought...or if this relation can be ruled out...(like, the drought preceded the eruption....).

so, what is your background/interest?
Chris