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.
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.
Stolen with permission from my cousin.
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?
But it would be great to find out, don't you think?