This is academic research at its most fun and it is to be found in a new book - Born to Rebel by Frank Sulloway - which claims to shed fresh light on a number of historical revolutions (intellectual as well as political) by describing them in terms of personality differences between first and later borns. Because of the domestic dynamics that shape their personality, first borns, says Sulloway, are more likely to be reactionary, orthodox and intolerant while the younger ones are radical, open to new ideas and gullible.
From reading this book you would never know that Sulloway is actually attempting, almost single-handedly, to revive a theory that has lain pretty well moribund after a devastating attack more than a decade ago and was the victim of another onslaught in a book published in America last year.
The idea that first-borns have special affinity for power and success has deep roots. While not holding a candle for the first born, Sulloway has presented an impressive range of historical data to support his claim that there are consistent and measurable differences between them and their siblings.
He shows, for instance, that during the Reformation, while 66 per cent of the Catholic martyrs executed in Protestant countries - ie reactionaries holding to the existing faith - were first born, an astonishing 96 per cent of the rebellious Protestant martyrs had been younger children. He finds the same predominance of second borns on the side of the rebels in the great Victorian intellectual and religious upheaval that centred around Darwin's theory of evolution.
In the book, the result of 26 years' work researching 20,000 biographies in 25 languages, it is younger children who are history's movers and shakers: Darwin, Marx, Lenin, Castro, Ho Chi Minh and Nelson Mandela were all later born. As indeed was John Major - no firebrand but compared with his brother he is the radical life and soul of the party.
Between 1700 and 1875, many hundreds of people expressed views on evolution. Throughout those years, evolution was seen as a radical, subversive doctrine. Individual later borns were 10 times more likely than first borns to believe in evolution, a difference that persisted until the late 19th century, when evolution at last became a respectable idea and the birth- order effect disappeared.
In all, Sulloway has tested his argument on 3,894 scientists, 893 members of the French National Convention during the Terror of 1793-94, the leaders of 62 different American reform movements, such as the abolition of slavery, and more than 700 protagonists in the Protestant Reformation in Europe. In each case, younger children were far more likely to support reform or revolution, while elder children were more likely to support reaction. In the late 16th century, for instance, later borns were twice as likely to embrace the Copernican theory that the earth revolves around the sun.
The effect is proportional to how radical the revolution is. Thus, Newtonian physics, which had fewer political and religious implications than Darwinian biology, was less strongly associated with younger children. Eugenics and spiritualism, which were reactionary movements, were actually led by first borns. Many theories, including psychoanalysis, relativity and Copernican astronomy, were supported by later borns when they were new and heretical, then defended by first borns when they became orthodoxy.
But while no one has yet challenged Sulloway's research directly, it has to be seen in context. Birth order has long been a popular area of research. There are about 2,000 books and journal articles in the literature. In the Sixties and Seventies no work on developmental psychology was complete without a mention that first borns tended to be more driven and ambitious and brighter but also more anxious conformist, while later borns were more sociable.
Then in 1983 the whole field came under deadly assault from a book by Cecil Ernst and Jules Angst. Birth order: Its Influence on Personality analysed a huge number of studies and concluded that most of them were so poorly designed and had so many flaws that no reliable conclusions could be drawn at all. This approach was continued in Separate Lives, by Judy Dunn, an expert on sibling relationships, and her husband Robert Plomin, behavioural geneticist, published in 1990. It declared that "individual differences in personality are not clearly linked to birth order [which] plays only a bit-part in the drama of sibling differences".
Even so the belief, certainly at a popular level, persisted. "If we regard scientific myths as basically akin to a belief in vampires," declares Professor Steven Peterson, of Alfred University, New York, "then it's quite clear that so far as birth-order theorists are concerned we have yet to find the functional equivalent for the crucifix, let alone the stake."
Last year his book Birth Order and Political Behaviour, co-written with Albert Somit and Alan Arwine (University Press of America), looked for birth-order effects, not among historical figures, but within today's political elite - and found none. Whether they looked at American presidents, Supreme Court justices, popes or British prime ministers, there were no more than the expected number of first borns but they did no better than later borns, either.
"There is an apparent excess of first borns among judges and senators," says Peterson "but once you control for education - parents do tend to put more resources into educating first borns - the difference vanishes. We even looked at West Point graduates. Military officers should show a higher percentage of first borns if there was a leadership connection, but they actually had fewer then average."
Of Sulloway's book he says: "It is probably one of the most rigorous efforts to determine the effects of birth order on people's behaviour. There are more than 50 studies on the impact of birth order on political behaviour and the results are mixed and inconsistent. It's too thin a reed upon which to base any large-scale theories of human behaviour"n
`Born to Rebel' by Frank Sulloway, published by Little Brown, price pounds 20.Reuse content