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The rate at which migrants are arriving has diminished considerably almost everywhere in Europe since the huge inflows seen in 2015. Yet migration continues to dominate political debate throughout the European Union. This suggests that populist, anti-immigrant sentiment is not actually being driven by claims that mainstream politicians cannot defend Europe’s frontiers.

The decline in new arrivals to Europe began well before anti-immigrant political leaders took power in Italy or immigration pressure nearly toppled Germany’s ruling coalition. It is largely the result of EU efforts, such as the agreement with Turkey to prevent Syrians from crossing into Greece, its cooperation with Libyan militias, and the massive pressure it has placed on the Sahara transit states to close their borders. Thanks to these measures, Europe has become a de facto fortress against migration.

So why does immigration remain at the top of many Europeans’ minds? The answer could be economic: those who arrived in 2015-2016 have already created labour-market imbalances, with low-skill immigrants increasingly competing for jobs with low-skill citizens. And it is true that in most of Europe, hostility toward foreigners runs deepest among low-skill workers.

Why the violence?

But there are reasons to believe that more than economic issues are at stake. For starters, anti-migration (more accurately, anti-foreigner) sentiment is beginning to be expressed violently, not just in Italy, where there have been several instances of shootings aimed at migrants, but even in generally well-ordered Germany.

Research shows that when there are significantly more men than women, the increased competition for female partners can lend itself to violence.

In the eastern German city of Chemnitz, violent clashes broke out recently between right-wing protesters and police and counter-demonstrators, following the killing of a German by two young men from Iraq and Syria. Support for the right-wing Alternative für Deutschland (AfD) party is strong in Chemnitz and the wider region, with most of the attacks on foreigners having occurred in the new Länder of the former East Germany.

Crime and unemployment cannot explain this eruption. Chemnitz is home to fewer foreigners than many similar-size German towns, and crime is generally under control there. Moreover, unemployment – which is declining throughout Germany – is not particularly high in Chemnitz, standing at 7 per cent.

The male-to-female ratios

But there is another potential explanation, rooted in evolutionary psychology. One trend that is rarely mentioned in migration discussions is the rise in the share of men among refugees and asylum-seekers. In the last three years, men – many of whom are aged 18-35 – comprised more than two-thirds of all people seeking protection in Germany. Whereas the total number of refugees as a share of Germany’s total population is small (2.5 per cent), refugees form a far larger share of Germany’s young male population.

The impact is particularly noticeable in eastern Germany, which already suffered from a gender imbalance – the male-to-female ratio among the younger cohorts approaches 115:100 in most parts of the region – because educated women have a much higher propensity than men to move to western Germany for higher-paid jobs. As a result, a significant share of eastern Germany’s young male population has little chance of finding a partner and starting a family.

Research shows that when there are significantly more men than women, the increased competition for female partners can lend itself to violence. One study links polygamy, which leaves low-status males without wives, to civil wars.

Countries like Germany that have recently admitted a large number of young male refugees will have to manage the fallout of the resulting societal shifts.

The implication is that hostility toward foreigners in eastern Germany – and perhaps across Europe – may be rooted partly in a primordial defensive response by local men, who want to protect their territory, including ‘their’ women, from other men. It is probably not a coincidence that Chemnitz, which has shown a readiness to vote for extremist parties, has the highest male-to-female ratio among 20-40-year-olds in all of Germany.

Managing societal shifts

Not all men are affected equally by this state of affairs. Since women tend to ‘marry up,’ or find partners with higher socioeconomic status, it is less educated and poorer men whose romantic prospects are most affected by an influx of male asylum-seekers. And, indeed, less educated and poorer groups tend to show the most opposition to migration.

Notably, the problems created by gender imbalances cannot be solved with better education or more income redistribution, because mating preferences are relative, not absolute. Those among the native population with the lowest incomes and education levels will always be worse off, if they have to compete with a large number of young male immigrants.

To be sure, gender imbalances are not the only driver of anti-immigrant sentiment, let alone populism more broadly. But evolutionary psychology, which stresses competition for females, can add another dimension to our understanding of these phenomena, while helping us to predict when and where civil strife might erupt.

There is little that can be done to change gender imbalances in a particular place. But, even if the problem cannot be ‘solved,’ understanding it might help to limit the damage, not least by enabling leaders to avoid policies that are either not useful or would exacerbate tensions. For example, restricting family reunion (to limit the number of foreigners) might make matters worse, because the male asylum-seekers would be more likely to be single and seek partners in the local population.

Countries like Germany that have recently admitted a large number of young male refugees will have to manage the fallout of the resulting societal shifts. Doing so effectively requires their leaders to recognise that those shifts are not just a matter of economics.

(c) Project Syndicate