In prehistoric times, the average hunter-gatherer is estimated to have had a life expectancy of around twenty to thirty years depending on local conditions.6 Despite an often more stable supply of food, the agricultural revolution did not improve this much, and according to some accounts reduced it, since larger, settled groups were more exposed to infectious disease and problems related to sanitation. In classical civilizations such as Ancient Greece and the Roman Empire, life expectancy has been estimated at around eighteen to twenty-five years. In medieval Britain, estimates range from
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