When an academic "discovers" what ordinary mortals have known for eons, it's called science.

Harvard political scientist Robert Putnam has found that diversity is not a strength, but a weakness; the greater the diversity in a community, the greater the distrust. Professor Putnam's five-year study was reported last year by the Financial Times and is finally percolating down to others in the media and across the blogosphere.

In diverse communities, Putnam observed, people "hunker down": They withdraw, have fewer "friends and confidants," distrust their neighbors regardless of the color of their skin, expect the worst from local leaders, volunteer and car-pool less, give less to charity and "agitate for social reform more," with little hope of success. They also huddle in front of the television. Activism alternates with escapism, unhappiness with ennui.

Trust was lowest in Los Angeles, "the most diverse human habitation in human history," a finding the "progressive" Putnam, who hangs out at Harvard, found perplexing. Almost as predictable is the manner in which these straightforward, sad findings are being misconstrued by puzzled pundits or pressure groups accustomed to maligning You Know Who.

The Commission for Racial Equality hasn't heard a word Putnam has said. "Separateness is becoming more entrenched in parts of our society," they warned ominously, in response, and hastened to rededicate themselves to "encouraging people from different communities to meet and understand one another."

Putnam, of course, said nothing about misunderstanding or roiling conflict. Diversity triggered not racial hostility but "anomie or social isolation," as he put it.

Writing for City Journal about the sad settings that Putnam excavated statistically, John Leo also introduced an error: "Social psychologists have long favored the optimistic hypothesis that contact between different ethnic and racial groups increases tolerance." Putnam makes it abundantly clear that he found no evidence of "bad race relations, or ethnically defined group hostility."

Rather, diversity generates withdrawal and isolation. The thousands of people surveyed were not intolerant, bigoted or even hostile; they were merely miserable. This is mass depression, the kind associated with loss, quiet resignation, and hopelessness.

Other perplexed pundits fingered multiculturalism and the failure to assimilate. Again, this is not what Putnam has unraveled. Not a word did he say about whether newcomers in the 41 U.S. localities studied fly Old Glory or are proficient in English – or whether these mattered at all. He merely examined the impact on trust and sociability of racial and ethnic diversity, only to find that it messes equally with men, women, conservatives, liberals, rich and poor. (He does concede that "the impact of diversity is definitely greater among whites.") There is nothing to implicate assimilation or lack thereof.