Log on to indulge your fantasy of immortality

Genealogy websites offer few hard facts but plenty to fuel people's dreams of a place in history, writes Matt Houlbrook.

Obsession with pornography and genealogy are the two dark desires on which the internet's success is built - and both play on our fantasies in similar ways. A quarter of all search engine requests are porn-related. A recent Sunday Times article claimed that "1.7 million UK surfers regularly visit family-history websites, making it one of the most popular online hobbies".

Four years ago, the National Archives put the records of the 1901 Census online. When the site went live, 1 million people visited in the first three hours, and the site crashed. The National Archives has since collaborated with a private company to publish census records for other years, the latest of which - from 1841 - was launched this week. We can now log on to Ancestry. co.uk and search for our forebears - providing we pay the £69.95 annual subscription fee. Genealogy, like sex, sells.

What do you get for your money? Ancestry's tag line is "Discover your family story" - yet there are very few "stories" to be discovered in the 1841 Census. Each entry provides a name and address or occupation, but beyond that information is frustratingly vague. Ages are rounded down to the nearest five years; places of birth are not given.

Websites such as this are invaluable in making archival material accessible to anyone with an interest in the past - the democratisation of history is something to celebrate, not condemn. But the census is the historical record at its coldest and most reticent. It gives no sense of the individuals behind the raw data. There is nothing of the messy, tragic or exciting nature of ordinary lives in the past. The furore surrounding the publication of census records is a lot of fuss about very little history.

Despite this, thousands of us will visit this and other family-history websites as we try to trace our ancestors. What drives this obsession with documents that are dry and often bland? In part, records such as the census are the raw materials through which to reconstruct a family tree - historical research as painstaking exercise in cataloguing and compiling.

In part, a name or address might be the clue that leads to other sources in which an individual's life emerges more fully. One of the successes of Channel 4's Not Forgotten series was its use of letters, diaries and newspapers to "turn those long lists of names (inscribed on Britain's Great War memorials) back into real people with real desires and potential... and celebrate their astonishing stories". Ultimately, however, public interest in "bare bones" records depends on precisely the lack of information they provide. Into the gaping holes in the archival record we project our fantasies about the past.

There has been considerable academic interest in the ways in which, as Patrick Wright, the cultural critic, puts it: "the national past is above all a modern past" - constantly told and retold to meet the demands of the present. Constructing a family past is the same kind of present-centred history-making, as documents become what Andrew Higson, professor of film studies at the University of East Anglia, calls "an imaginary object" on to which contemporary values and anxieties are transferred. Discovering our surname in a census document or on a war memorial allows us to project ourselves into 1841 or 1916. Immortalised in the public record, that becomes a powerful confirmation of our existence, giving us secure roots in an increasingly rootless world. More than this, when we look at our ancestors' names we try to imagine who they were - but in so doing we and they become one and the same. This is why many of us will pay to use Ancestry.co.uk. Perhaps, deep down, we do not want to know about the individuals behind the names: to know more would disrupt the fantasy lives that sustain us today.

When the 1901 Census went online, I searched for Houlbrooks living in Mexborough, the South Yorkshire town where my family come from. There were several, including 23-year-old Ernest - "filler coal mine". More recently, I looked for my name on the local war memorial; it was there, only with an "H" in front of it. For a middle-class academic historian, temporarily escaping into these very different and almost exotic pasts offers weird - and somewhat illicit - pleasures. To be honest, I know nothing about either of these men, though I am sure that the lives they lived were far richer than those I created for them. As the 1841 Census is published, we should remember that in projecting our own fantasies on to stark columns of names, we risk losing sight of their remarkable yet unseen stories.

Matt Houlbrook is lecturer in 20th-century British history at Liverpool University. His book Queer London: Perils and Pleasures in the Sexual Metropolis, 1918-57 (University of Chicago Press, £20.50) is Longman-History Today book of the year.