Science has discovered the facial hair that women are most attracted to

Not all beards were created equal, at least when it comes to attracting women.

According to a 2013 Australian study, the most attractive beard length is "heavy stubble," which comes after about 10 days of growth.

Fascinatingly, heavy beards, light stubble, and clean shaven were all equally less attractive than heavy stubble.

The science says that each length of beard sends a different signal.

"Facial hair correlates not only with maturity and masculinity, but also with dominance and aggression," write authors Barnaby J. Dixson and Robert C. Brooks.

"An intermediate level of beardedness is most attractive, while full-bearded men may be perceived as better fathers who could protect and invest in offspring," they write.

Beyond attractiveness, researchers also found that facial hair affects perceived fertility as well. The more facial hair a man had, the more masculine a woman perceived him to be - especially when she was in the fertile phase of her menstrual cycle.

Dixson and Brooks came to their conclusions by showing pictures of 10 smiling men at different stages of beard growth to 351 women and 177 heterosexual men.

As the Register UK observed, evolution is at work here.

"Beardedness is a prehistoric condition," reported science writer Rik Myslewski, who argues that beards have long been a "strong indication of maleness surrounding puberty."

Therein lies the magnetic power of the beard.

"Thus, beard quality, thickness, and fullness would signal to potential mates that he was sexually mature and prepared for fatherhood," Myslewski writes. "This makes beardedness a sexual characteristic that is potent to women."