As you know, I covered the super-volcanoes in "Man and Impact in the Americas". The climatic effects will vary depending on the type of ejecta, but they seem to have been gradual, allowing people time to get to sheltered areas with high food stuffs, and simply not as fatal as impact climate collapses, from what can be made out from the gross physiological record.

One problem, Raoul, is with the genetic change clocks, and everyone is using different ones. I think mapping the effects of the massive impacts are going to help towards sorting the clocks out.

Another problem is making inferences about populations from the limited sample of sites. For Homo Sapaiens or Homo Neanderthalis, I don't think we really have enough sites to map the effects of the Toba eruption accurately. Even rough guesses of the total Neanderthal populations are tough to come by.

While there is little doubt that the Toba eruption was "unpleasant", Homo Sapiens seems to have done well, expanding into Europe and the Americas a short time later. Of course, with modern population densities, the effects of one of these eruptions today will likely be quite bad.

All of that said, that is information from before my stroke, and thus is parts of my brain not affected by it. While I am functioning well this morning, I doubt if I will be able to do that kind of work again.