“What is clear is that the sex ratio would have been substantially biased and increasing through time, and even small amounts of bias can have a big effect,” he said.

“In a population where just a few powerful older men are able to have multiple concubines you end up with a large number of young single men quite rapidly. Some men would have two to three wives, but the Norse sagas say that some princes had limitless numbers.

“So raiding was away to build up wealth and power. Men could gain a place in society, and the chance for wives if they took part in raids and proved their masculinity and came back wealthy.

“Because polygynous marriage increases male-male competition by creating a pool of unmarried men, it increases risky status-elevating behaviour.”

Surprisingly the idea was first put forward by the Norman historian Dudo of Saint Quentin who argued in his 10th century work, The History of The Normans, that the Viking raids were sparked by an excess of unmarried young men.

Similarly the English antiquarian William Camden in his 1610 work Britannia suggested that the ‘Wikings’ were selected from areas of overpopulation after they "multiply’d themselves to a burdensome community".