It is particularly important to note that the bust following the initial farming boom is found in two historically separate agricultural expansions, the first into Central Europe c. 7,500 years ago and the second into Northwest Europe 1,500 years later. It is possible that some of these regional declines represent out-migration to neighbouring areas rather than a real decline in numbers, for example, from the Paris Basin into Britain, but, in some cases, for example, Ireland, Scotland and Wessex, it is very clear that the rising and falling trends are roughly synchronous with one another—there is little indication of one going up as the others go down. On present evidence the decline in the initially raised population levels following the introduction of agriculture does not seem to be climate-related, but of course this still leaves open a variety of possible causes that remain to be explored in the future. One possibility is disease, as the reference to the Black Death above implies, although this would have to be occurring on multiple occasions at different times in different places, given the patterns shown. It is perhaps more likely that it arose from endogenous causes; for example, rapid population growth driven by farming to unsustainable levels, soil depletion or erosion arising from early farming practices, or simply the risk arising from relying on a small number of exploitable species32. However, these suggestions remain speculative and an autocorrelation analysis of the demographic data did not find evidence of a cyclical pattern, which would be one indicator of the operation of endogenous processes (Supplementary Fig. S7). Regardless of the cause, collapsing Neolithic populations must have had a major impact on social, economic and cultural processes.
Nature Communications 4, Article number: 2486 doi:10.1038/ncomms3486
Regional population collapse followed initial agriculture booms in mid-Holocene Europe
Stephen Shennan et al.
Following its initial arrival in SE Europe 8,500 years ago agriculture spread throughout the continent, changing food production and consumption patterns and increasing population densities. Here we show that, in contrast to the steady population growth usually assumed, the introduction of agriculture into Europe was followed by a boom-and-bust pattern in the density of regional populations. We demonstrate that summed calibrated radiocarbon date distributions and simulation can be used to test the significance of these demographic booms and busts in the context of uncertainty in the radiocarbon date calibration curve and archaeological sampling. We report these results for Central and Northwest Europe between 8,000 and 4,000 cal. BP and investigate the relationship between these patterns and climate. However, we find no evidence to support a relationship. Our results thus suggest that the demographic patterns may have arisen from endogenous causes, although this remains speculative.