There’s been a lot of discussion recently about older fathers and their DNA. An Icelandic study led by Kari Stefansson, published in Nature and explained more clearly for us lay people here in The Guardian.
Men produce sperm throughout their lives (unlike women, whose eggs are all there by the time they are born), and as they age, men produce a higher (though still very small) number of mutations that pass to their children. Stefansson’s team looked at 78 trios (i.e. father, mother and child) and found that ‘a 20-year-old father transmits, on average, around 25 mutations…whereas a 40-year-old father transmits around 65.’ Every additional year at the time of conception adds an average 2 further mutations.
It’s an interesting finding, even though the number of mutations in the father’s DNA is only a tiny fraction of the total. Journalists have extrapolated from the finding to suggest that it may explain rising levels of certain diseases, such as autism and schizophrenia, because the age at which men father children is rising.
This seems to me rather a leap to make, based on a sample of only 78 fathers – and from Iceland, one of the most homogeneous populations in the world. Nor is it all that clear what role genes play in conditions such as autism and schizophrenia, although there are certainly some problems that are caused by a genetic mutation, such as Fragile-X syndrome.
I can’t comment on the science, or the statistics, but the other assumption in this story is that fathers are now older than they used to be. It’s true, more or less, that first time fathers in 2012 are older than first time fathers in 1900, or 1950, or ever 1980. But the assumption that most children were once born to younger men is wrong.
A hundred years ago, men and women married earlier, had their first child 9 or so months later, and then continued to have children until the mother reached menopause or died, quite possibly in childbirth. If only because they needed help to raise their motherless brood, widowers usually married again, so they might well start another family when they were in their 40s or 50s. Henry Parkes, Premier of New South Wales, married 3 times, and his youngest son Cobden, was born when he was 77.
Without effective contraception, Anthony Trollope’s description of the poor clergyman Mr Quiverful and his 12 children, is not unusual – or only unusual in that all these children survived. Large families were expensive. In the middle class, in particular, men often delayed marriage until they could afford to pay for the large household that would almost inevitably follow, complete with servants and private education.
Arthur Hughes, The Long Engagement (1859). Typical of the narrative pictures Victorians loved, this shows a curate and his fiancée who are still waiting to marry, long after they carved their initials in the tree – because they must wait until he gets a decent paying job. Birmingham City Art Gallery (from Wikipedia Commons)
Did these older fathers produce more defective genes in their DNA? Who knows, but there is one notorious example of a defective gene – haemophilia – that impacted on European history, and it is very likely that the problem can be traced to an older father.
In the early 19th century, the British royal succession was in a mess. George III and his wife Charlotte had a large family, 6 daughters and 9 sons, but only one legitimate grandchild. Under the Royal Marriages Act of 1772, no member of the royal family could marry without the king’s consent – and this proved very difficult to acquire, particularly for his 6 daughters, who were kept under close confinement in ‘the nunnery’ – the Palace at Kew.
His eldest son, George, Prince of Wales, fell in love with a Catholic widow, Maria Fitzherbert. The 1701 Act of Settlement excluded Catholics from the succession (this would trip up Prince Charles and Camilla one day too). Despite this, they married illegally in 1785, but if there were offspring of the union, they remained a closely guarded secret.
Ten years later, desperately short of money because of his extravagant building projects, George agreed to another marriage, to his Protestant cousin Caroline of Brunswick. In return for Parliament agreed to pay his debts. It was hate at first sight. George was apparently too drunk to consummate the marriage that night, but the next morning he performed his duty – twice, according to later report – and never entered the marriage bed again. Fortunately for the nation, exactly 9 months later, Caroline gave birth to Charlotte, Princess of Wales.
George’s brothers were even less uxorious. Frederick, Duke of York, separated from his childless wife to live with his mistress. William, Duke of Clarence, lived for 20 years with an actress, Dorothy Jordan, who produced 10 little FitzClarences – all while continuing to act on the stage. Edward, Duke of Kent, lived with a series of mistresses.
Of the younger brothers, Augustus, Duke of Sussex, and Ernest, Duke of Cumberland, married and had children – but in both cases, the status of the marriage was unclear: Augustus married Lady Augusta Murray without his father’s permission in 1793, while Ernest married his cousin, Frederica, in 1815, following her divorce from her German husband (and his subsequent, perhaps too convenient, death). The youngest son, Adophus, Duke of Cambridge, was still unmarried when disaster struck, in 1817.
By then George III and his wife had produced 15 children – but only one legitimate grandchild, Charlotte, Princess of Wales. In May 1816, she married Prince Leopold of Saxe-Coburg-Saalfeld, and died giving birth to a stillborn son on 6 November 1817. Suddenly, England had no heir.
What followed was an unseemly scramble by George III’s unmarried sons to produce a replacement heir. William, 53, married Adelaide of Saxe-Meiningen, 25 in July 1818; Edward, 50, married Victoria of Saxe-Coburg-Saalfeld, 31, on 29 May 1818; Adolphus, 44, married Augusta of Hesse, 23, in June 1818.
And the winner was –
The Duchess of Kent (1786-1861) and her daughter Victoria (1819-1901). (Photo credit: Wikipedia)
Edward’s wife, Victoria, gave birth to a daughter, Princess Alexandrina Victoria, on 24 May 1819. Eighteen years later, she was crowned Queen Victoria. At the time of her conception, Victoria’s father was 50. We can’t know for sure, but it is widely believed that Edward left his daughter a deadly genetic inheritance.
Haemophilia is a terrible genetic disorder where the blood does not clot. It is carried on a single gene on the X chromosome. It is recessive, so it rarely occurs in a woman (XX) but half a woman’s eggs will carry the defective X chromosome. If that defective chromosome appears in her sons (XY), they will have haemophilia, and if it appears in her daughters, those daughters will carry the same risk down through the next generation.
Haemophilia and colour-blindness are both examples of a recessive gene on the X chromosome.
Queen Victoria carried the gene, and through her, haemophilia entered the royal bloodlines of Europe. There are details of her family tree here. The most politically significant link was through her granddaughter, Alix, who married the Russian Tsar Nicholas II. Their only son was a haemophiliac, and the Tsarina’s fears for him seem to have put her under the influence of the strange cult-like figure of Rasputin, who she believed could stop her son’s episodes of uncontrolled bleeding. Rasputin’s influence within the court led to his assassination in 1916.
The politics of the Russian Revolution are far too complex to attribute to a single cause – but this dynastic crisis played at least a small role in the events that followed. It is strange to think that it can be traced to another dynastic crisis, in England, nearly a century earlier.
This time last year:
Food Riots, 22 September 2011
Historians are Past Caring 