Pregnancy is a miraculous thing. The human body is designed to expel whatever that is strange or foreign to it; that's the
basis of our immune system (yes, our bodies are racist, get over it). But here we have an infestation of an organism (or even more) with half of its genetic material coming from a foreign source, and the woman's body adapts to
nourishing and
protecting it (except in
rare cases).
When the time comes, the foreign organism makes the host's body expel it, with a great deal of labour (ahem) and pain. Et voila! A baby is now born. A helpless, piteously mewling little thing that is completely dependent on the former host (if lucky, and host's partner) for everything from food, water to shelter.
And for the most part, the host is supportive and protective.
O_____o
I mean, this organism has made your life difficult for the best part of nine months, takes it's own sweet time to get out with
much effort and discomfort on your part, and you welcome it with open arms? Superficially, it doesn't sound logical to grow attached and wanting ferociously to take care of what is, essentially, a parasite on your physiological and material resources.
But you do and that is thanks to the bonding molecule,
oxytocin. No, not superglue.
Oxytocin doesn't just make a mother tend to be more nurturing (particularly breastfeeding mum), but it can also be stimulated in others. Visual cues such as a baby's cuteness, is thought to elicit the hypothalamus to produce oxytocin, making us want to coo and cuddle the adorkable little things.
To wit, my current source of oxytocin tsunami.

Escape artist have escaped the swaddling.
Dinner with mummy, post bath.
Tea time with big sister.
Oxytocin has also been implicated in development of trust and relationship-building behaviour. It appears that
oxytocin starvation leads to impaired moral conduct. Could we one day modulate antisocial behaviour with judicious application of oxytocin?
Who knows?
But it would be great to find out, don't you think?