The theory was discredited thanks to the advent of genetics. But now, writing in the journal Ecology and Evolution, scientists have suggested flings can influence the offspring of future mates.

Professor Russell Bonduriansky, of the University of New South Wales in Australia, said: ‘Traditionally, the idea is when this type of mating takes place, there is no resource transfer and there is no paternal care.

‘Males contribute DNA to fertilise an egg, but we believe there is something more complex going on.’

His researchers began thinking about evolutionary preferences for seminal fluid in 2014 while studying the offspring of female fruit flies that mated with males of varying sizes.

They found if a male, either large or small, mated with a female fly before she was fertile, he would pass his sperm along, but the immature eggs would not be fertilized.