PARIS — For 70 years now, we've been living in peace. Badly hit by an economic crisis, obsessed with signs of a decline, undermined by a pessimism without equal in the world, the French forget what joy it is to live in a pacified country and continent. Not everybody is so lucky.

If conflicts between countries have grown scarcer since World War II, the same can't be said of civil wars. They have killed more than 15 million people since the Allied victory in 1945. In the last half-century, civil wars have affected one in every four country — even in Europe in the late 1990s.

These conflicts cause immense pain, wreak economic havoc for years, destroy cities and lives. They also create terrible migration patterns, as evidenced at the moment south of the Mediterranean, where Syrians, Eritreans, Somalis, Malians, Sudanese and Central Africans leave to head towards Europe. Last year, more than 230,000 migrants are estimated to have landed on the Old Continent's coasts, driven out of their countries by bloody conflicts and persecution.

Of course, each war has its history and roots. But all civil wars have a common cause: a major opposition between groups that can't be solved through political institutions. It's essential to understand where this opposition originates if we are to avoid these immense losses.

Over the last quarter-century, many researchers have worked on this topic, but their results have been inconclusive. They have assessed the impact of religious, linguistic and ethnic differences on conflict risks. Others have gone further and have looked at genetics and, more precisely, at the correlation between genetic diversity and the risk of war.

Two economists, Tufts University's Enrico Spolaore and the University of California's Romain Wacziarg. argued in a 2013 article that the closer the population of two countries are genetically, the greater the chance that they will go to war with each other. They explain this link with a simple hypothesis, namely that similar peoples want the same resources and are therefore more likely to fight to get their hands on them.

In an article entitled, "The Nature of Conflict," published last month, three scientists made an opposite correlation in the case of civil wars. Quamrul Ashraf of Williams College, Cemal Arbatli of Moscow's Higher School of Economics, and Oded Galor, an Israeli professor at Brown University, wrote that "genetic diversity, as determined predominantly during the exodus of humans from Africa tens of thousands of years ago, has contributed significantly to the frequency, incidence and onset of both overall and ethnic civil conflict over the last half-century." 

For example, the probability of civil war emerging between the years 1960 and 2008 was five times higher in countries with significant genetic diversity (such as the Democratic Republic of the Congo) than in countries with very little diversity (such as South Korea).

The researchers offered three main explanations. First of all, genetic diversity can be detrimental to the establishment of trust and cooperation. We are suspicious of those who don't look like us. Secondly, groups that are genetically different often have different political priorities in terms of producing wealth and goods either for the public or for their redistribution. Finally, "Since genetic diversity reflects an heterogeneity between individuals — through character traits rewarded differently depending on the geographical, institutional or technological surroundings — it can exacerbate economic-inequality-induced grievances," they wrote.

Fatalistic findings

There's something breathtaking about this research. The reasoning behind it sometimes resembles a shaky footbridge. The work "borders on full racism," one anonymous economist commented online. And its conclusions can lead to fatalism. What good is there in trying to prevent civil wars if they originate in human migrations that took place tens of thousands of years ago?

This research can also raise questions about its authors, but Oded Galor, the most seasoned of the three, is a renowned economist. For 20 years, he has been editor of the Journal of Economic Growth, one of the world's most-respected economic publications. For years he has been nurturing an interest in the millennial roots of economic growth. And if he recently began to study genetic diversity with Quamrul Ashraf, it's because it's a factor in this very long-term growth.

Having been the targets of violent criticism after an article they published in 2009, the two told Nature that they believed the study of genetic diversity was "a proxy for immeasurable cultural, historical and biological factors that influence economies."

Be that as it may, we'll have to get used to seeing scientific progress influence how we view the world, the economy and human societies. Instead of giving in to fatalism, this could instead prove to be yet another reason to forge institutions for preserving peace.