December 1, 2010 – Women instinctively shun their fathers when they are most fertile, even as they seek out the companionship of their mothers, a new study has shown.

The reasons, say the researchers, is evolution. Females in other species have also been observed to give a wide birth to male kin during periods of maximum fertility.

“The behaviour has long been explained as a means of avoiding inbreeding and the negative consequences associated with it,” explained lead author Debra Lieberman, a professor at the University of Miami.

“But until we conducted our study, nobody knew whether a similar pattern occurred in women.”

Lieberman and colleagues examined cell phone records of 48 women in their reproductive years, noting the date and duration of all calls with their fathers and, separately, their mothers over the course of a billing period.

They found that women called their dads less frequently during the days when the were ovulating, and would hang up sooner if the calls came the other way.

Overall, daughters were half as likely to ring up papa during high fertility days compared to the period of menstruation. What’s more, the conversations that did occur lasted about half as long.

The researchers checked to be sure that the women were not giving their dads the slip in order to meet male suitors.

Nor were they simply trying to evade parental control: even when hormones were working overtime, the women were far more, rather than less, likely to give mom a ring.

Women have hard-wired mechanisms that protect against the risk of less healthy children, which tend to occur when close genetic relatives mate, the researchers concluded.

“It makes sense that women would reduce their interactions with male genetic relatives, who are undesirable mates,” Lieberman said.

At the same time, when women are in their most fertile phase they are attracted to men with “masculine” qualities such as husky voices and competitive personalities, previous research has shown.

The study was published in the peer-reviewed journal Psychological Science.