Birth control pills work by providing your body with a dose of estrogen and progesterone that prevents ovulations. Like everything we put inside our bodies, it’s effect is not specific to the reproductive organs, but rather a generalized effect. It is also worth noting that hormones can work as neurotransmitters, affecting the brain and nervous system directly.
The hypothalamus regulates what we call the 4 F’s: fighting, fleeing, feeding, and mating. In the first half of the 1990’s, scientist Simon LeVay found a nucleus in the hypothalamus that has a statistically significant difference between sexes, the INAH3. Later on, he found that the difference has more to do with sexual orientation than sexual identity.
Out of 166 human societies that have been studied, romantic love has been found in around 90% of them. This serves as evidence that romantic love is not only a staple of the human condition, but beyond that it seems to have an evolutionary advantage. If not, it would not have evolved independently in different cultures.