I should have been more specific. There wasn’t a single event that triggered human evolution, since that would imply that human evolution was static until and when such an event occurred. The processes of evolution are ongoing. An event such as an eruption that wipes out a large population, leaving pockets of survivors here and there, would not change the overall pace of evolution. Rather, the different pockets of survivors would each evolve in their own direction, rather than in the direction of the larger group.
Such a drastic loss from the gene pool would drastically alter any “pace” or direction of evolution, if there is such a thing.
One cannot postulate that a putative evolution of the human species was either static or dynamic prior to the super volcanic eruption of Toba, since there is no found surviving evidence either way.
Further, for the survivors of Toba to be able to generate successful descendants, they would have had to be a single group, else there would have been too few for a successful gene pool - and we would not exist.
No one today has any experience with super volcanic eruptions and the survival of the human species. All scenarios from a Yellowstone eruption would be pretty much a ELE for modern humans, despite our technology or maybe because of it.
Prior to Toba there were many drastic events, which could have done all sorts of things to our species. Our present human species could have been around since 250,000 BC.
There is even some uncertainty as to what exactly did the solar system look like millions of years ago, and the Earth's place in it.