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| Where's the damn ketchup? |
Dr Thomas and his colleagues also rely on a mathematical model. They are trying to explain the pattern of apparent false-starts to modern human culture. The species is now believed to have emerged 150,000-200,000 years ago in Africa and to have begun spreading to the rest of the world about 60,000 years ago. But signs of modern culture, such as shell beads for necklaces, the use of pigments and delicate, sophisticated tools like bone harpoons, do not appear until 90,000 years ago. They then disappear, before popping up again (and also sometimes disappearing), until they really get going around 35,000 years ago in Europe.
The team drew on an earlier insight that it requires a certain number of people to maintain skills and knowledge in a population. Below this level, random effects can be important. The probability of useful inventions being made is low and if only a few have the skills to fabricate the new inventions, they may die without having passed on their knowledge.
According to Dr Thomas, therefore, culture was not invented once, when people had become clever enough, and then gradually built up into the edifice it is today. Rather, it came and went as the population waxed and waned. Since the invention of agriculture, of course, the population has done nothing but wax. The consequences are all around you.
