A new research has found that women who grow up with a younger brother tend to lose their virginity nearly two years later than otherwise because of their traditional care-giving roles.

Researchers said that elder girls were more likely to take on the role of helping with family chores and as a result were less likely to form sexual relationships.

“Elder daughters may provide more help to their parents in raising their younger brothers than elder brothers,” said study authors Fritha Milne and Debra Judge, of Western Australia University. “Associated with this prolonged help is a delay in sexual activity and thus a delay in potential for starting their own family.”

The researchers studied 273 people aged 18 to 75 and found girls with exclusively elder brothers were almost a year older when they had their first period than those with no older siblings or those with only elder sisters. And girls with only younger brothers were on average almost two years older when they first had sex than those with no younger siblings. The findings were published in Proceedings of the Royal Society B.

Scientists in the Salzburg University have found that the contraceptive pill has the potential to increase the grey matter inside your head to make you smarter. Their study has shown that contraceptive pills enhance the brain’s ‘conversation hub’ and memory. It increases brain size by around 3 per cent.

Scientists, who took high-resolution images of the brain, found that several areas in the brain looked larger for women who took the pill, irrespective of the brand or formulation of the drug, or how long it had been prescribed for.

These areas seemed to be the ones that dealt with social skills and memory. “The behavioural changes due to contraceptive use are likely to affect those skills that are already better developed in women compared to men like, for example, memory,” said Dr Belinda Pletzer of Salzburg University.

One theory as to why the pill affects the brain this way is that the oestrogen or progesterone used to stop eggs from being released also strengthens the links between nerve cells in the brain. The study is published in the journal Brain Research.