The Economists in The proper study of mankind writes:
SEVEN hundred and forty centuries ago, give or take a few, the skies darkened and the Earth caught a cold. Toba, a volcano in Sumatra, had exploded with the sort of eruptive force that convulses the planet only once every few million years. The skies stayed dark for six years, so much dust did the eruption throw into the atmosphere. It was a dismal time to be alive and, if Stanley Ambrose of the University of Illinois is right, the chances were you would be dead soon. In particular, the population of one species, known to modern science as Homo sapiens, plummeted to perhaps 2,000 individuals.
The proverbial Martian, looking at that darkened Earth, would probably have given long odds against these peculiar apes making much impact on the future. True, they had mastered the art of tool-making, but so had several of their contemporaries. True, too, their curious grunts allowed them to collaborate in surprisingly sophisticated ways. But those advantages came at a huge price, for their brains were voracious consumers of energy—a mere 2% of the body’s tissue absorbing 20% of its food intake. An interesting evolutionary experiment, then, but surely a blind alley.