To fully understand this, we have to dig deep into the psychological roots of attraction.

On an evolutionary level, the basic survival roles taken on by humans are a very useful tool to rationalise the subconscious factors when deciding on attractiveness.  We are trained, whether we like it or not, to pick good genetic stock to ensure the continuation of our species.

Hunter-Gatherers:  Traditionally the males.  Should be strong, intelligent, able to solve problems.  Navigation skills for returning to shelter or areas of good food and resources.  Manual dexterity for creating tools.  Protective, monogamous.  These are all traits that 90% of women will subconsciously find attractive in a potential mate.

Nest-Builders:  Traditionally the females.  Should be caring, hard-working and fertile.  Indicators of good child-bearing skills include wide pelvic structure for childbirth, narrow waist derived from fitness through high-stamina activities, large breasts to ensure adequate nutrition for the baby, and large, wide eyes for avoiding danger.  These are all traits that 90% of men will (sub)consciously find attractive in a potential mate.

Although these two roles may seem very black-and-white in terms of being gender-specific, it isn’t that easy.  The hormones that govern which of these traits you have, and which you find attractive, do not necessarily match up to the physical bits you are given at birth.  And none of this is binary: that is to say, not just one or the other.  Every human is on one sliding scale with degrees all the way from ‘Football Fan Lager Swilling Beast’ right down to ‘Pink Fluffy Teddy Loving Sweetie’.

Why is any of this important?

Because all of these attraction factors are gender-biased, except the most important one.

When there is a dangerous situation, what is the sense that can keep you out of trouble?  What would it be a hard struggle to raise offspring without?  What enables early man to be a valid contributor to the community?  Vision.  Eyes are the ultimate communicator, the most vital sense, and if anything happened then you would become a burden to the tribe.  This is true for both sexes.  So how can you ensure that your potential mate, male or female, is going to have a long and prosperous life of good vision?

Eyelashes.

Eyelashes are the protection mechanism to keep dirt, infectious matter, seeds, bugs, foreign objects and anything harmful out of the eye.  The longer and thicker the eyelashes, the better protected they are.  Without even realising it, everyone finds people with long eyelashes attractive.  It’s the entire reason mascara was invented. Nestor Carbonell (Richard from Lost) is a prime example of eyelash-driven gay icon status.  Have you ever wondered why the stereotype is that French and Spanish men like Antonio Banderas are more attractive to both women AND men?  It’s not the tan, or the muscles.  It’s the eyelashes.