Britain is still buzzing over Anglican Archbishop Rowan Williams’ remarks on the inevitability — and advisability — of granting some recognition to Sharia law. Not only has the Archbishop inspired a seemingly endless stream of mostly angry weekend op-eds and news stories, the backlash has given government minister Phil Woolas the courage to kick off a debate over Muslim cousin marriage.

Unfortunately, by focusing the cousin marriage question on the problem of birth defects, Woolas has missed the most important issue. Woolas has received some significant support, but has also stirred up a furious backlash from Muslims, who’ve demanded his resignation. That would be a disaster, since it would make open discussion of cousin marriage problem even more taboo than it’s been up to now. Sacking Woolas would also undo whatever good the uprising against the Archbishop’s remarks has done.

Archbishop Williams makes an easy target for the country’s anxieties over failed Muslim assimilation. No-one’s afraid of retaliation from this gentle patriarch. Yet the same government officials who rebuke Williams and argue that Sharia law contradicts British values say nothing about Britain’s recent decision to grant welfare benefits to spouses in foreign polygamous marriages. It’s one thing to decry Williams’s remarks on Sharia, and quite another to openly oppose polygamy and cousin marriage. So while Williams may have temporarily broken the conspiracy of silence on the problems of failed Muslim integration, action on the polygamy and cousin marriage issues will be the test of what, if anything, has actually changed.

While Woolas has raised the question of birth defects, the most serious concern is that cousin marriage blocks assimilation. (I show how in “Assimilation Studies” and “Assimilation Studies, Part II.”) That is why cousin marriage poses a genuine threat to Britain’s survival as a nation. The most spectacular example is today’s report that surveillance planes in Afghanistan have picked up the voices of Taliban fighters speaking in, for example, Bradford accents. Bradford is a virtual “reverse colony” within Britain, a city that has for all practical purposes transformed into a section of Pakistan. And as I explain in “Assimilation Studies,” this enclave was essentially built through cousin marriage. Now the Taliban draws recruits from the children of these unassimilated Pakistani immigrants.

For all the outrage stirred up by Woolas’s comments on “inbreeding,” it may actually be easier to talk about cousin marriage’s harm to young children than to directly acknowledge that cousin marriage is the mainspring of failed Muslim assimilation. As a proxy for the most serious issue, the birth defect debate has both advantages and disadvantages. The physical harm of cousin marriage is real, yet its extent and significance are debatable.

Honest defenders of cousin marriage acknowledge that there are ill effects. The favorite statistic is that an expected rate of around two percent for severe or fatal birth defects is doubled to four percent in the case of first cousin marriages. This, it is argued, is a limited harm, not significantly greater than the increased risk faced when women over 40 bear children. If we don’t ban the latter, why ban the former? It’s also suggested that genetic counseling can counteract the increased risk.

There are problems with this argument, however. Most studies that yield the 2/4 percent figures focus on defects noted in the first year of life. Examine the first five years and we are looking at an average rate of four percent severe defects or death in the general population, which jumps to eight percent in British South Asians with high rates of cousin marriage. Some put the risk figure for children of cousin-marriage among British Pakistanis as high as 10 percent.

We also have to reckon with huge prevalence rates of cousin marriage among Pakistani immigrants in Britain, especially immigrants from rural areas. Depending on how it’s counted and who is being counted, the rates of cousin marriage can reach well over fifty or even sixty percent. There also seems to be an effect from many generations of cousin marriage. In one study, 69 percent of the British Pakistani couples were related and 57 percent were first cousins. But when the relationship of parents was factored in, the degree of relationship was as if 70 percent of the couples had been married first cousins.

The massive prevalence of cousin marriage among certain sections of the British Pakistani population means that the already substantial effects on children are magnified greatly. The result is that, in debate, we see statistics framed in ways that make the problem seem very large or very small. Double or more a rate of risk is impressive, but we are still dealing with a small (but real) minority of children. But while only a minority of children of cousin marriages are effected, the sheer number of cousin marriages means that a hugely disproportionate share of British children with birth defects are born to Pakistani immigrants and their descendants. So the argument goes back and forth, with each side framing statistics in its own way.

It’s a fair and important debate, but it also happens to miss the critical issue of the effect of cousin marriage on assimilation. It is on this that Britain’s fate actually hinges. That is why Woolas must not be sacked, and why a cousin marriage debate must proceed.