Adam Kuper's thesis is that "marriage within the family - between cousins or between in-laws - was a characteristic strategy of the new bourgeoisie, which had a great deal to do with the success of some of the most important Victorian clans".
He further argues that, at a time when most businesses carried the burden of unlimited liability, it made perfect sense to ensure that the enterprise remained firmly within the control of family members, who could be more readily trusted than new entrants to the clan. These are interesting ideas, but the evidence he produces is unconvincing.
Thus, a whole chapter is devoted to the Bloomsbury Group. There was a good deal of sleeping around among that strange and diverse cast of characters, but little if any intermarriage of any consequence; moreover, the group's members showed very little interest in anything as vulgar as business, and in many cases would have been very upset to hear themselves described as "bourgeois".
In this year of Darwin, it was inevitable that the tendency of Darwins and Wedgwoods to marry one another over the generations would be examined in some detail. The great Charles himself was interested in the problems, if any, that could arise from the marriage of cousins, and wanted a question on the subject to be included in the 1871 Census so that he could calculate whether such liaisons were likely to produce a higher incidence of mental illness and other conditions.
The proposal was turned down by Parliament, possibly influenced by the fact that Queen Victoria had married her cousin, the Prince Consort, whom she still mourned. Marriage within families was certainly common within the royal houses of Europe.
Charles' son George then carried out a survey of his own, with a mixture of diligence and ingenuity of which few but a Darwin would have been capable. He found no evidence that marriages between cousins produced ill-conditioned offspring.
The reference to "characteristic strategy" in Kuper's initial explanation of his thesis implies that there was something deliberate about the choice of relatives in marriage, but he provides other, more convincing explanations of the phenomenon. He reminds the reader that, in an age when chaperones were considered essential for young unrelated couples, cousins had more opportunities to be alone together.
The interesting chapter on "The Family Business" observes that many of the people considered here were Quakers, and indeed Kuper could have concluded that friendships nurtured at Quaker meetings were a more likely explanation of their tendency to marry one another than any "strategy" to protect family interests. Perhaps they just liked one another.
Likewise, the chapter devoted to "Wilberforce and the Clapham Sect" could have suggested that people with common values, such as a fierce opposition to slavery, who meet frequently to pursue their common goals are likely to generate intimate friendships.
There are many gems in this book. Henry VIII puts in an appearance, having had the law changed to permit him to marry, briefly and disastrously, Catherine Howard, who was Anne Boleyn's cousin. The first woman in Britain to obtain a divorce, Jane Addison in 1801, did so by proving that her husband had slept with her sister, thus ruling out further intercourse on the grounds of incest.
Jane Austen also appears here, with the explanation that in Pride and Prejudice (1813), Mr Bennett has four daughters. The poor man had five, as most readers of this book will know, and as the editor should have known. And is it really true that one in ten wives had trust funds in the middle of the 19th century?
Kuper should have called his book Networking in 19th-Century England, but that wouldn't have been a very catchy title, would it?
Incest and Influence: The Private Life of Bourgeois England
By Adam Kuper. Harvard University Press. 304pp, £20.95. ISBN 9780674035898. Published 29 October 2009