Feminine beauty, the subject of philosophical and artistic musings for millennia, can be predicted by something as basic as hormones – in women, but not men. Researchers at the University of St Andrews in Fife, UK, have found that women’s facial attractiveness is directly related to their oestrogen levels.

Miriam Law Smith and colleagues photographed 59 women, aged between 18 and 25, every week for six weeks. On each occasion, they provided a urine sample for hormone analysis and gave information on where they were in their menstrual cycle. None of the women wore make-up, nor were they taking the contraceptive pill.

The researchers then selected the photograph of each woman that had been taken at the time of her highest urine-oestrogen level. As expected, this correlated to the point of ovulation in the women’s menstrual cycles. These photographs were rated by 14 men and 15 women, also aged 18 to 25, for attractiveness, health and femininity.

The group also rated two composite face images. One composite was an amalgamation of the 10 women with the lowest peak-oestrogen levels, while the other image was a combination of the 10 women with the highest levels.