The Sunday afternoon neighborhood Facebook drama started with a post of two photos. "Okay, I found this bone in an alley," the caption read. "This looks like part of a human femur, but I'm hoping to be wrong. Is there a dog chewing bone that look like this?"

There is indeed. The photos clearly showed an old beef knuckle, dirty and weathered, but easily identifiable for any owner of a large dog. Also, cows and people are not the same size — if this bone was human, it belonged to Goliath.

"Could be a dog bone," allowed the first comment, "but it also looks like human bone." The next four commenters agreed, recommending a call to the police and pleading for updates on the investigation. Some skeptics finally arrived to propose the beef knuckle solution, but an officer had already been summoned to the scene.

About 40 escalating comments deep, the thread was closed, but not before someone felt a need to suggest the bone was from a murder attributable not to the (majority white) neighborhood in which it was found, but rather to a "cold case" from the (majority minority) neighborhood a few blocks east. (Note: I live in Minnesota. Contra Fargo, there aren't lot of unsolved dismemberment cases around here.) Crime lab results are probably not forthcoming.

The Great Beef Knuckle Mystery of 2019 is Facebook neighborhood groups in a nutshell: Chatty drama, disagreements about dog waste, crime paranoia, and low-key (or, occasionally, not so low-key) racism are standard fare.

But for all their flaws, these groups (and their analogues on apps like Nextdoor) have their value. As often as they are weird or contentious, they are friendly and useful. Newcomers are heartily welcomed; recommendations for local shops and services are freely shared; desperate appeals for rescue when your car is stuck in the snow are speedily answered, often by total strangers.

While the umpteenth "gunshots or fireworks?" conversation on July 5 always threatens to change my mind, a reasonably healthy neighborhood group strikes me as an asset — not an ideal source of community connection, certainly, but far better than the silence its absence could produce.

I speak from the experience of membership in three such groups. One is a two-neighborhood buy/borrow/barter page where I have successfully rid myself of items including a box spring, fabric scraps, and dirt — yes, actual dirt — while acquiring Lincoln Logs, bikes, and slightly old lettuce for my guinea pigs to munch. The second is the group for my neighborhood proper. Until recently it was barely active, but now it buzzes with lost-and-found pets, community events, and frequent digital summonses of the local city council member to account for civic grievances large and small.

The third group, home of the Beef Knuckle Mystery, is by far the most entertaining. It's technically for the next neighborhood over, but dual membership is common, as both are small geographic areas and we share the buy/borrow/barter space.

This community is peak Facebook neighborhood group. The dog poop disposal debates have slowed of late, but the urban turkey sightings, requests for recommendations that have already been given a dozen times, and earnest pleas for all fireworks to be canceled on Independence Day because they make little Fluffy-Poo scared will surely never die. Each year has its recurring rhythm of topics: gardening in the spring; crime in the summer; Halloween in the fall; snow removal in the winter. Then there are the perennial favorites, like solicitations of advice for handling various vermin or inquiries into whether you should call the cops because a man you do not know has knocked on your front door.

This familiarity makes it no less odd to me that we've built an online community composed entirely of people already part of an actual, physical community. Why do we choose to have these conversations on Facebook when we could have so many of them in person? Why do we gather in a digital group instead of at the street corner or on someone's front porch?

Part of the answer is simple convenience and busyness: Facebook lets us participate in the neighborhood gossip from work or school or church or wherever. But I suspect there's also something bigger going on, that our decision to digitize neighborhood life is at least somewhat influenced by (and, in turn, influential for) declining levels of social trust, increasing feelings of loneliness and isolation, and the downward trend of community participation exhaustively detailed in Robert D. Putnam's Bowling Alone:

For the first two thirds of the 20th century a powerful tide bore Americans into ever deeper engagement in the life of their communities, but a few decades ago — silently, without warning — that tide reversed and we were overtaken by a treacherous rip current. Without at first noticing, we have been pulled apart from each other and from our communities. [Robert D. Putnam, Bowling Alone]

Perhaps we feel some lingering impulse or obligation to engage our neighbors, a holdover from a friendlier age, but we've lost (or never learned) the skills to do so in real life. A Facebook group can lower the barrier to interaction. It lets us check people out before risking an in-person meeting, and we can encounter a larger number of neighbors than we'd likely ever meet offline.

That's a good thing — and yet it must also be admitted that those encounters are typically shallow, that digital distance makes space for rudeness, even cruelty, we'd rightly quash during ordinary conversation, and that online interactions can become a replacement for real community life as much as they can be its support.

The Facebook neighborhood group is often amusing — my Sunday afternoon was decidedly enhanced by being able to laugh at the beef knuckle sleuths — but it is also a "good servant but a bad master." It should always be made to build the community it serves, never to subvert it.