The Obamas: The Untold Story of an African Family by Peter Firstbrook Crown, 333 pp., $26.00

Families, it sometimes seems, are just a vast web of potential embarrassments…interspersed, no doubt, with the occasional opportunity for pride.1 Honor and shame, as much as love or liking, are what bind us to our kith and kin. The teenager rolls her eyes as her mother gets up to dance at the wedding; grandparents flush when their friends ask about the grandson who just “came out” in Sunday school; a wife looks down disconsolately as her intoxicated husband rises to make the after-dinner speech. We can all evoke such moments.

As for the upside: remember Aunt Rose kvelling—that wonderful Yiddish word, derived from the German Quelle, a spring, which gives just the right sense of gushing with pleasure—over her nephew’s medical degree, or those “Proud Parents of an Honor Student” bumper stickers. You may not love or like, or even know, Mary-Jane, but her kinship, once avowed, can bring you a warm glow when she wins an Oscar. “She’s my cousin,” you say to anyone who will listen. (You may not reclaim her when the stories about her rehab turn up in the tabloids, but you feel a moment of panic when your coworkers gossip about her. Do they remember Oscar night?)

Still, in the United States, it’s easy to escape your wider family. Families have contracted; the claims of kin are increasingly optional. Ancestor hunting is one of the more harmless addictions enabled by the Internet, but many Americans still couldn’t give the maiden name of both their grandmothers. In much of the rest of the world—as for most of human history—the web of kinship is rather stickier. It doesn’t just tell you who shares your “blood”; it helps fix who you are and explain why you are the way you are.

In rural Africa, certainly, things are still pretty much as they used to be everywhere. People keep track of their significant relatives and ancestors, in accordance with local rules of kinship. In most African societies, the tracing is patrilineal, running, like surnames in England, through the paternal line. Of course, mostly the people who will listen to these family histories are already family, or contemplating marrying into it. For these stories to gain a wider audience, a relative would have to achieve something truly worth kvelling over.

The British documentary maker Peter Firstbrook stepped into one of these large patrilineal clans when he arrived in Kenya, in late November 2008, to scout materials for a film about the president-elect’s Kenyan background. As he got to know the relatives of the new leader of the free world, they told him who they were in the way that was most natural to them: by connecting themselves backward in time to their ancestors.