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After the domestication of animals and crops in the Near East some 11,000 years ago, farming had reached much of central Europe by 7500 years before the present. The extent to which these early European farmers were immigrants or descendants of resident hunter-gatherers who had adopted farming has been widely debated. We compared new mitochondrial DNA (mtDNA) sequences from late European hunter-gatherer skeletons with those from early farmers and from modern Europeans. We find large genetic differences between all three groups that cannot be explained by population continuity alone. Most (82%) of the ancient hunter-gatherers share mtDNA types that are relatively rare in central Europeans today. Together, these analyses provide persuasive evidence that the first farmers were not the descendants of local hunter-gatherers but immigrated into central Europe at the onset of the Neolithic.

Managing future flood risk is necessary to minimize costs and achieve maximum benefit from investment. This study presents a framework to assess urban structural protection under climate change and socio-economic development. Floods cause billions of dollars of damage each year 1 , and flood risks are expected to increase due to socio-economic development, subsidence, and climate change 2 , 3 , 4 . Implementing additional flood risk management measures can limit losses, protecting people and livelihoods 5 . Whilst several models have been developed to assess global-scale river-flood risk 2 , 4 , 6 , 7 , 8 , methods for evaluating flood risk management investments globally are lacking 9 . Here, we present a framework for assessing costs and benefits of structural flood protection measures in urban areas around the world. We demonstrate its use under different assumptions of current and future climate change and socio-economic development. Under these assumptions, investments in dykes may be economically attractive for reducing risk in large parts of the world, but not everywhere. In some regions, economically efficient investments could reduce future flood risk below today’s levels, in spite of climate change and economic growth. We also demonstrate the sensitivity of the results to different assumptions and parameters. The framework can be used to identify regions where river-flood protection investments should be prioritized, or where other risk-reducing strategies should be emphasized.

Traditional cost-benefit analyses (CBAs) of flood risk reduction measures usually ignore distributions of damages over populations, which disadvantages the poor. Instead, a CBA based on social welfare includes individual social vulnerability through relative impacts on consumption. If vulnerabilities are high, floods are catastrophic and cause poverty, migration or indirect deaths, and risk reductions have high social welfare values. For non-catastrophic risks, social welfare values of risks are relatively higher for vulnerable low-income households. We present a framework to integrate social vulnerability into CBAs, and show how financial protection reduces social flood vulnerability and provides welfare benefits. A case study illustrates that traditional CBAs underestimate the social welfare value of flood risk reduction measures, up to a factor of 30. Data on financial protection is however scarce, which hampers estimation of the social welfare value in practice. A solution is to increase financial protection of individuals, in addition to offering physical flood protection.