Nice guys really do finish first when it comes to getting the girl, says a new research.
According to psychologists, traits such as selflessness and altruism have become part of our genetic make-up because they were attractive to mates.
They believe that as humans evolved, qualities such as being fittest and strongest were usurped by other qualities - such as offering a helping hand in bringing up the children.
"The expansion of the human brain would have greatly increased the cost of raising children so it would have been important for our ancestors to choose mates both willing and able to be good, long-term parents," the Telegraph quoted Dr Tim Phillips and colleagues from the University of Nottingham and Institute of Psychiatry, King's College, London, as saying.
"Displays of altruism could well have provided accurate clues to this and so led to a link between human altruism and sexual selection."
The study, which investigated whether altruistic behaviour evolved as a result of sexual selection, involved 70 identical and 87 non-identical female twin pairs.
They completed questionnaires relating to their own levels of altruism by answering questions such as "have you given money to charity?" and "have you dived into a river to save someone from drowning?".
They then asked them if they would find the same qualities desirable in potential mates.
Statistical analysis of their responses suggested that, in our evolutionary past, those with a stronger mate preference towards altruistic behaviour mated more frequently with more altruistic people.
That means that altruistic genes would be more prevalent than selfish genes.
"These results are consistent with a link between human altruism towards non-relatives and sexual selection and throws an exciting new light on the puzzle of altruistic behaviour - which appears, at first sight, to be at odds with evolutionary theory," Dr Phillips said.
The results were published in the British Journal of Psychology.