Most of those who live in the North Caucasus are caught somewhere in the middle: between a perpetually fearful state that is wary of the independent power base even peaceful Salafism represents and the Islamist rebels who, by simply asking for a package of bandages or a piece of stale bread before they return to the mountains, make them a target for the police. Local authorities have responded with paranoid and indiscriminate crackdowns, treating every Salafist as a potential terrorist. Moscow is largely out of energy and ideas; the conflict may have crossed into a state of intractability.

It remains unclear how much of this history had to do with the bombs in Boston. The fact that two young men of Chechen origin committed an act of terror is not the same as saying Chechen terrorism has come to United States. Mr Kadyrov, usually spectacularly unreliable in his pronouncements, may have gotten it more or less right when he suggested via his Instagram account (his preferred method of communication these days) that the “roots” of Dzhokhar and Tamarlan’s “evil” are best found in America, not Chechnya.

In the end, whatever twisted sense of grievance and fury that drove the Tsarnaevs may have found its ultimate trigger in their adopted homeland more than in the one of their memory. Dzhokhar and Tamarlan are Chechen and Muslim, but they are also immigrant young men, struggling with their own sense of isolation and frustration. The language and motifs of the Caucasus militancy may have acted as a kind of salve, however desperate, for whatever dislocation they felt in America. Their uncle, who lives in Maryland, called the brothers “losers” who didn’t know what to make of themselves in America and thus were left “hating everyone who did”.

And so, in Boston, the cultivated sense of grievance and justification of the North Caucasus militants may been infused with the feelings of loneliness and revenge found in American men who commit acts of horrific violence: a case of “Beslan meets Columbine”, with disastrous results. If al-Qaeda and American male-rage have anything in common, it is that both foster the sort of self-obsessed nihilism that can have tragically bloody results. “I don’t have a single American friend,” Tamerlan is quoted as saying in a photo essay that followed his aspirations as a competitive boxer. “I don’t understand them.” Now it is America struggling to understand the Tsarnaevs.

A male dental assistant, Mr. Alquicira is in the minority. But he is also part of a distinctive, if little noticed, shift in workplace gender patterns. Over the last decade, men have begun flocking to fields long the province of women.

Mr. Alquicira, 21, graduated from high school in a desolate job market, one in which the traditional opportunities, like construction and manufacturing, for young men without a college degree had dried up. After career counselors told him that medical fields were growing, he borrowed money for an eight-month training course. Since then, he has had no trouble finding jobs that pay $12 or $13 an hour.

He gave little thought to the fact that more than 90 percent of dental assistants and hygienists are women. But then, young men like Mr. Alquicira have come of age in a world of inverted expectations, where women far outpace men in earning degrees and tend to hold jobs that have turned out to be, by and large, more stable, more difficult to outsource, and more likely to grow.

“The way I look at it,” Mr. Alquicira explained, without a hint of awareness that he was turning the tables on a time-honored feminist creed, “is that anything, basically, that a woman can do, a guy can do.”

Last one, then I’m out. Most broad in its coverage of the different issues at play: how Saverin compares to the rest of the founders, what exactly his investments have been, locals hoping for star sightings, etc.