It was conceived by Aristotle and dismissed as superstition in the late 19th century.

Now, the idea that physical traits of a mother's previous partner can be passed on to future children has been given a scientific foundation.

The study is the first to prove that the theory of heredity, known as telegony, exists in the animal kingdom.

Scientists discovered that, for fruit flies at least, the size of the young was determined by the size of the first male the mother mated with, rather than the second male that sired the offspring.

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They mated immature female flies with a large or small male. Once the females matured they mated them again and found that they produced larger offspring even when mated with a small male.

The researchers, of the University of New South Wales, propose that the effect is due to molecules in the semen of the first mate being absorbed by the female's immature eggs where they influence future offspring.

Dr Angela Crean, the lead author, said: "Various non-genetic inheritance mechanisms make it possible for environmental factors to influence characteristics of a child.

"Our new findings take this to a whole new level - showing a male can also transmit some of his acquired features to offspring sired by other males."

She added: "But we don't know yet whether this applies to other species."

The study is published in the journal Ecology Letters.

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