One would think, to some degree, reunions will become a thing of the past in the age of social networking, especially class reunions. After all, part of the fun is to find out what everyone else has been up to; with everyone on Facebook, we already know all of that.

Yet we’re a gregarious species by nature, and looking at pictures on a monitor and chatting by Skype is still no substitute.

So we gather together from time to time to look at old photos

and take new ones. Decades separate the two photos, and children who barely make it to their mothers’ waistline now have children who have children who have children. Even when only a relative handful of them gets together, they fill the frame easily.

Several of them are, for all intents and purposes, strangers. Grandchildren of great uncles, cousins removed by years and geography. Yet just say the word “family” and strangers are no longer so distant, and introductions come easily.

If only we could learn that as species.