The Toba “super volcanic” eruption 74,000 years ago had a massive impact on human evolution. In size it dwarfed Krakatoa and Tambora emitting 2,800 cubic km (about 670 cubic miles) of ash and lava or about about 200 times larger than Krakatoa. It cooled the earth by ~3 C for a period of about 10 years. Parts of Indonesia, India and the Indian Ocean were covered by 15 centimeters of volcanic debris. Human populations outside Africa suffered severely in the short term due to food shortages. Some have estimated that just a few thousands individuals survived this period. Our DNA today is all derived from this small pool.
Volcanoes cool the planet by increasing global albedo and cutting out sunlight. Their imprint can be seen in the current global temperature data.
Luckily Toba is not due to erupt again for another 600,000 years!