I just read your 2003 article, "Cousin Marriage Conundrum." You're right on the money about Iraq. I am at the end of my 1 year tour in Iraq serving as a military advisor to an Iraqi Army brigade in the northern Kurdish Region. From my observations, it is clear to me that Iraqi obsession with sect and tribe is a major obstacle to reconciliation and development. Of the two, I must say that I believe sectarianism is the greater challenge, based upon my observations during 110 days in Baghdad with my Iraqi Brigade. But even this is related to tribalism, in that sectarianism as practiced in Iraq has little to do with belief (although shia and sunni do have different beliefs) and much to do with group identity — for the average Shia and Sunni are simply tags to identify group membership much more than flashpoints for theological debate. This sectarian group consciousness has become so heightened that Arabs I meet even in safe S_______ will only reveal their sect after great prodding, for fear of retalion (interestingly, this same phenomenon prevailed in Somalia when I was their 15 years ago — in that extremely clannish culture, it is considered very impolite to ask someone about their clan affiliation, and even my local hire interpreter dodged telling me what his clan was — I still do not know to this day).
On the other hand, pure tribal identity still plays a big role in Iraq. You can see this in evidence in Anbar, where attacks against Coalition and Iraqi Government forces have dropped precipitously after the tribal sheyks determined that Al Qaida was a bigger threat than the US and decided to forge an alliance with us. Another example is in the northern region, where the Iraqi units tasked with defending oil infrastructure were recruited locally, and do nothing to stop attacks on that very infrastructure, because most of the attackers are their relatives and fellow tribesmen.
There is an interesting counterpoint to the enduring nature of tribal loyalty in Iraq, however, and that is the Kurdish Region. As late as the 1960s tribal affiliation was still the dominate social identity for many Kurds - even to the point that the Iraqi regime was able to rally sizeable armed support against the Kurdish rebellion from among the Kurds themselves, by exploiting tribal rivalries and wooing tribal aghas and chiefs. Even as late as the early to mid-1970s, the great Kurdish leader, Mullah Mustafa Barzani, derived most of his power from his tribal base rather than from a political constituency (even though he was president of the Kurdish Democratic Party). Now however, a completely different situation prevails. While the tribes still exist and have some influence, they have mostly been emasculated of any real power. Furthermore, Kurds almost universally identify more with their ethnic identity than with any other source of identity, be it tribe, sect, religious affiliation (christian, Yezidi, Kakiye, etc) or State citizenship. However, all is not roses - to a certain extent, political party affiliation has supplanted tribal affiliation as a claimant to allegiance and a source of patronage, with the two main parties - the Kurdish Democratic Party led by Kurdish Regional Government President Massoud Barzani (son of Mullah Mustafa) and the Patriotic Union of Kurdistan headed by Iraqi President Jalal Talabani. Needless to say, the vast power of these two parties has led to friction - even major violence as in the civil war in the mid- to late 1990s — and corruption. That said, the Kurdish Region is far better developed politically, socially, and economically than the rest of Iraq, due in no small measure to the leadership of these two parties. So the chains of tribalism can be broken, as they have been in the Kurdish region.
It doesn't always turn out this well, however. Somalia is another interesting case in point. Here, the power of traditional tribal elders was broken by the erection of the superstructure of the modern nation-state over the country. When this government was overthrown in 1992, people still identified themselves by clan, but the traditional clan leaders had lost all influence. The result - any s***head kid with an AK-47 suddenly was the real power in town - and tended to use that power against other people from rival tribes.