If paying celebrities to go galivanting around the world finding out more about their relatives was all it did, then Who Do You Think You Are?

(BBC One, Wednesday, 9pm) would be a pretty despicable programme. Why don't the celebrities fund their own research? Why on earth should we pay for them to sit in the archives and cry over the sad lives of their ancestors? Could it be that a celebrity tear isn't worth shedding unless there's a camera pointing at it?

The truth is that, as well as all this celebrity introspection, there has always been another level to the programme, one that tells the wider social story of Britain and explores not only how much we have changed over the past 150 years or so, but also how much we haven't.

Last week's programme, featuring the singer Annie Lennox, was a good example. Lennox grew up in Aberdeen and went back there to find out more about her family. After a lot of clumping around the cold, grey streets, she discovered that her great-great-great grandmother Mary had been a pauper, living in a dark, blackened room up a discouraging close. To survive, Mary had to rely on poor relief, the Victorian equivalent of the benefits system, and it was here that some of the most striking parallels between then and now emerged.

Poor relief was based on the idea that the poor could be divided into two categories: deserving and undeserving, and you were only deserving if you could prove you were unable, rather than unwilling, to work. Those who did apply for the relief were taken in front of sombre church hearings in which well-fed men in tight dog collars made their judgment. Even if the judgment was favourable, the poor relief would always be set at the bare minimum so as not to encourage idleness.

Lennox was shocked when she heard this – it seemed, she said, like a dark Victorian melodrama. But the facts of the story don't require a lot of retuning to sound more current. We are in the middle of a debate right now about the benefits system and the questions are the same. Is it too soft? Does it encourage the idle in their joblessness? The language may be different but the implication is the same: there are some poor people who are lazy and must be forced out of their idleness.

The effect of all this on Lennox was clear. Wrapped up in a big scarf to protect her against the dour Aberdeen winds, she said the story of her family, and Victorian society, was now more clearly focused for her. "It ceases to be a fiction or an abstraction," she said. "The Victorian times in Scotland were incredibly tough."

But perhaps there was another, more positive message to be learned from the programme. If Who Do You Think You Are? proves anything, it's that most families, a few generations back, were affected by poverty; most of us lived in the dark. But in the 1970s and 1980s, millions of us escaped, Lennox included. She was part of the first generation in which most people had genuine comfort. Perhaps looking back on the dark, frightening history of Victorian poverty should remind us of that most of all.