But bring up the same reasons for getting biomass off the earth and you get funny looks. As if some people can't get their minds around the fact that disaster happens and if all of your species is on the same planet it only takes one really large catastrophic incident to finish the lot of us off for good. If this theory is right we came within an ace of extinction 70 thousand years ago ..
According to the Toba catastrophe theory, a massive volcanic eruption severely reduced the human population. This may have occurred when around 70–75,000 years ago the Toba caldera in Indonesia underwent an eruption of category 8 (or "mega-colossal") on the Volcanic Explosivity Index. This released energy equivalent to about one gigatonTNT, three thousand times greater than the 1980 eruption of Mount St. Helens. According to Ambrose, this reduced the average global temperature by 3 to 3.5 degrees Celsius for several years and may possibly have triggered an ice age.
Some geological evidence and computed models support the plausibility of the Toba catastrophe theory, and genetic evidence suggests that all humans alive today, despite their apparent variety, are descended from a very small population, perhaps between 1,000 and 10,000 individuals [3].
Reduce the effective human population size too far and we end up on the ugly line heading into the celler, and not the perky upward trending line. Which would be uncool.
