See that map above, from Transparency International, the anti-corruption watchdog group? The darker the color on the map, the more corrupt the country. Corruption is the norm around the world; northwest European societies, with their relatively low levels of corruption, are the outliers.
The connection between corruption and ‘familism’ has long been advanced, for example by Edward Banfield in his 1958 study of southern Italy, The Moral Basis of a Backward Society . [note: Parts of southern Italy did practice cousin marriage then; see above.] In a nutshell, the higher your loyalty toward your family group (be it nuclear, extended, clan, or tribe), the lower your loyalty toward the larger society, i.e. everyone outside your family group. The Brazilian social anthropologist Roberto DaMatta sums up the attitude this way:
‘If I am buying from or selling to a relative, I neither seek profit nor concern myself with money. The same can happen in a transaction with a friend. But, if I am dealing with a stranger, then there are no rules, other than the one of exploiting him to the utmost.’
In the harshest possible terms: Corrupt, nepotistic societies are that way because, from top to bottom, they are full of corrupt, nepotistic people. In different terms: People in such societies have much stronger family ties than Northwest Europeans, with all the good (old people taken care of at home, lower suicide rates) and the bad (large-scale nepotism and bribery). The biggest lesson for international policy-makers is that one cannot graft a policy from one people to another without grafting the people itself. And that way lies colonialism–as Greece’s current conundrum shows.
Because that’s an HBD site, they speculate that “inbreeding” (e.g., marriages between cousins) might have caused a supposed altruism gene to stay out of the gene pool in those ethnic and regional groups. I don’t know from altruism genes, but it seems to me sufficient to say that culture — nurture, not nature — is the culprit.
In any case, despite the HBD crowd’s concerns, the nature-vs-nurture thing is beside the point I wish to make here, and that is this: there are clear and unambiguous cultural differences that have a dramatic impact on the levels of corruption across societies — and that show why a project like the euro is so unworkable.
Moreover, I wonder if those more clannish societies are more “socialist” in the sense that few people can ever get really rich, individually, but nor can they get too poor either, because there’s always the family to look after you. This, versus what we have, in which it is possible to do very, very well individually, but you get old and die alone. An American friend who spent a lot of time in Italy told me that he loves the Italian way of life on so many levels. He said he couldn’t live there, because the frustration of everyday life — the inefficiency, the corruption, etc. — drove him crazy. But the Italians, in his view, may pay a significant price for their ways, but they derive non-monetary benefits that my American friend envied. This is somewhat analogous to my experience in Louisiana. We are poor and corrupt relative to most of America, but man, the people here are so wonderful in so many ways that you can’t put a dollar value on.
Finally on this topic, Spiegel  did an interview with Greek novelist Nikos Dimou, who said:
SPIEGEL: More than 30 years ago, you said in a SPIEGEL interview that in difficult moments of their history, Greeks always seek fault with others and never with themselves.
Dimou: That’s still true. When you talk to people here, they say, this Angela Merkel, this Schäuble (ed’s note: the German finance minister), why did they do this to us? I respond, “What does Merkel have to do with us? Nothing. We ran up these debts and asked the EU for help. That’s why they’re here.” Then the person I’m talking to usually replies that the Europeans are making good money off all this, or that it’s a conspiracy against Greece by the banks or by global capitalism.
SPIEGEL: Which could reflect another Greek trait you describe in your book, the tendency to overdo things.
Dimou: Precisely. We like to live beyond our means. You see this zest for life if you read (Nikos Kazantzakis’ novel) “Zorba the Greek” — we want to have everything, enjoy everything. The tendency to overdo things is also closely connected to a tendency toward repression. Greece is the home not only of democracy, but also of tragedy. The tragic hero is a person who overreaches himself, and violates the natural order of things.
SPIEGEL: Can Germans and Greeks ever hope to get along, despite their differences?
Dimou: Yes, they can, if they complement each other. The Greeks need the Germans because they can do things the Greeks can’t, and the Germans need the Greeks because they have this zest for life that makes the Germans happy.
Do the Germans see Greece as an indispensable part of their identity? So much that they’re willing to pay through the nose to support the weaker brother? It’s hard for me to see that, given the fundamental lack of felt cultural unity there. It’s all well and good to say “we’re all Europeans,” but how far does that really go? To be precise, how can you get people of nations that do not operate under the “familism” system described above — that is, nations that are not clannish — to feel a sense of connection and obligation to other nations such that they’re willing to spend till it hurts?