"mouselike creatures are among the small minority of mammals — less than 5 percent — who share humans’ propensity for monogamy. When a female prairie vole’s brain is artificially infused with oxytocin, a hormone that produces some of the same neural rewards as nicotine and cocaine, she’ll quickly become attached to the nearest male. A related hormone, vasopressin, creates urges for bonding and nesting when it is injected in male voles (or naturally activated by sex). After Dr. Young found that male voles with a genetically limited vasopressin response were less likely to find mates, Swedish researchers reported that men with a similar genetic tendency were less likely to get married"

so after all it is all in the chemistry...

lol.....isn't there a website devoted to that?....chemistry.com?
kidding

There aint no cure for love
There aint no cure for love
All the rocket ships are climbing through the sky
The holy books are open wide
The doctors working day and night
But theyll never ever find that cure for love
There aint no drink no drug
(ah tell them, angels)
Theres nothing pure enough to be a cure for love

- Leonard