I was covering only the period in England from 4000 to 6000 years ago when agriculture first established here, so relatively unaffected by those factors.Apart from periods of climate change or migration, when the opposite would apply.
Nick
As well as migration, in the historically most sparsely populated parts of the world, the Sahara, Mongolia, Kurdistan and Australia for example, nomads were commonplace, travelling cyclic routes with "hand me down" knowledge gained over long periods.
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