I am weighing in late on the HBO’s “Girls” phenomenon. There have already been various and valid concerns about the show for its racially monochromatic casting. (For some of the most thoughtful criticism on this point, see Dodai Stewart’s “Why We Need to Keep Talking About the White Girls on Girls”, Kendra James’ “Dear Lena Dunham: I Exist” and Jenna Wortham’s “Where (My) Girls At?”)

Nevertheless, I wanted to watch a few episodes and understand how its interior world worked before belatedly entering the fray.

But the show’s writer, director and leading actress, Lena Dunham, beat me to the punch. In an interview with NPR this week, she responded to the criticism by way of authenticity: “I really wrote the show from a gut-level place, and each character was a piece of me or based on someone close to me. And only later did I realize that it was four white girls.”

Using autobiography as defense, Dunham sought to nullify concerns about why she set an all-white cast in one of the most diverse cities in the world. At first, it made writerly sense to me. It was her gut. Her subconscious. An absence in her imagination.

An accident.

But then one line stood out: “Each character was a piece of me or based on someone close to me.” Sadly, Dunham seems to have no women of color “close” to her. And yet, she is hardly unique, because for all our talk about the multiracialism of the millennial generation, friendship segregation in high schools, colleges and, yes, even in Brooklyn, is more than a coincidence. It is a crisis.

Recent data has shown that while a substantial number of whites and blacks claim to have interracial friends, when asked to list the names of their close friends, only 6 percent of whites and 15.2 percent of blacks actually listed a friend of another race.

In her book Talking To Strangers, political scientist Danielle Allen says this is caused by “interracial distrust,” the negative feelings, such as fear, that limit the interactions people of different racial and ethnic lines have with one another.

In turn, such groups do not only perceive each other as “strangers” who should not be trusted, but end up creating racially homogenous economic networks and social capital as a result. In our racially stratified society, such differences do not mean “separate but equal” as friends, but decreased access to quality healthcare, education, jobs and political representation for communities of color.

Segregated friendship also has structural origins. In their 2006 report, “Residential Segregation and Interracial Friendships in Schools,” sociologists Ted Mouw and Barbara Entwisle found that patterns of friendship segregation seem to parallel those for residential segregation.

For young people, “residential segregation is important because it results in school segregation,” Mouw and Entwisle write, “which restricts opportunities for interracial friendship.”

Unfortunately, most American school districts are decreasing their efforts to desegregate schools, while school segregation is rising for Africa-Americans and Latinos. And with the conservative Supreme Court revisiting the constitutionality of affirmative action this summer, we can assume that this tragic trend will continue on college campuses across the country.

So, when Dunham confesses that “I always want to avoid rendering an experience I can’t speak to accurately.” We realize that her experiences growing up in New York and attending a super-liberal arts college were enough. For some reason, these progressive enclaves did not prepare her to live in a world with women of color as peers, as muses and as one of the girls.

It’s not too late to include such complexity as the show progresses. But the bigger question is, why were there no women of color in that world in the first place?