The Out of Africa Crowd May Shit A Brick

[Anomalocaris]

Toba catastrophe says nothing about whether there were other populations of the HSS, HNS, or Homo Erectus on the earth at the time, or how they were effected by Toba

Exactly...it says nothing and there is no evidence suggesting that HNS suffered similar devastation. We are constantly bombarded with disaster scenarios from nuclear winters due to asteroids or volcanoes but they are general in their effect and threaten lots of species. Why Toba would only effect HSS defies explanation.

Chronological distribution of fossils is not nearly uniform enough for us to pick up the Toba catastrophe from the samples of HSS or HNS fossils we have. If all we have are HSS fossils, we would have no evidence that HSS suffered Toba devastation either. All Toba evidence comes from genetic analysis. Since our genetic evidence for HNS are not nearly as complete as those for living HSS, It's no surprise if a major population decline amongst HNS could have escaped our notice.

All Toba scenario said was that particular breeding population of humans that contributes the most to our current gene pool had very few breeding pairs 79000 years ago. It didn't imply that particular breeding population was wide in geographic distribution, or included a substantial percentage of all HSS then lived. All it said is that particular population was severely effected. I can think of many modern examples where a particular local population might be severely effected by an distant volcanic upheaval, but the human species and the biota in general did see any drastic impact. Take for example the eruption of the Laki volcano in Iceland in 1783. This eruption ejected 100 million tons of sulfur dioxide into the atmosphere which weakened the Indian Ocean Monsoon of the 1783-1784. This led to diminished rainfall in Nile River basin, a severe draught and famine in Egypt, and the death 20% of the population of Egypt through starvation that year. In total Laki killed around 3 million people in Egypt. But the world wide human population certainly didn't see any noticeable decline during the same time. But if by happenstance Egyptian population were to later contribute disproportionally to subsequent human gene pool, then it would be recorded in later human genes that the human lineage suffered a population bottleneck in 1783.

Now consider Toba eruption was 200 time more powerful than Laki, it should not be surprising that such an eruption might cause some extremely severe local weather disruptions that would kill far more than 20% of the human population in certain areas. But just as Laki caused severe population effects in some areas but no global extinction event, there is no need to insist any Toba effect must be accompanied by global extinction detectable in fossil records.