Scientists know that women gravitate to men who have a different immune system from theirs.

We evolved in a tropical climate where the smells of plants and flowers were all around us. We spent a lot of time in the trees with a lot of sunlight and no clothes.

Men have a psychological need to show off their courage and strength. When he sees you talking to another guy, that instinct kicks in and he jumps to protect you and prove he's worthy of your love.

When you look at the brain regions associated with picking up data from the body, a huge amount of the brain is devoted to picking up information from the lips and tongue.

Women, it turns out, are built to lead - particularly in the modern world.

Today, American women bear an average of 2.2 children that live to adulthood. Across most of Europe, women bear even fewer young.

Blushing is thought to be linked to increased levels of norepinephrine in the brain, which may be associated with romantic feelings. It signals that we are interested and excited, which is attractive to men.