Wilson's "On Human Nature" should be required reading (and is shorter/more readable than Sociobiology)
I think it is an evolved response. According to attached, this is just an activated attachment system.
[Pair-Bonding, Romantic Love, and Evolution](http://journals.sagepub.com/doi/pdf/10.1177/1745691614561683 Attached
I think I'll leave this rationalist book right here
http://www.amazon.com/On-Human-Nature-Preface-Revised/dp/0674016386
On Human Nature by E.O. Wilson