The scientific reason newborns smell so lovely

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When any of my friends have babies, they know I will be front and centre busting to visit them in the hospital.

Sure, I want to see the new tiny human they created and make cooing noises and them, and listen to their super long, involved birth story, complete with all the blood and guts details that everyone forgets after the first month or so. But more than that, I want to sniff their baby's head.

Newborn baby head: there is no other smell like it.

The scent only lasts a few weeks, and then it's replaced by general baby smell, which is less pleasing because it encompasses poo and milky vomit.

Nobody actually knows what causes the unique smell in newborns, but the most popular theory is that it has something to do with vernix caseosa, the white substance babies are covered in while their still in utero, and sometimes when they're first born.

But we do now know the reason it's there: evolution.

Anatomy professor Johannes Frasnelli told New York Magazine that the newborn scent is designed to stop us leaving our baby under a tree and nicking off to the beach in those challenging first weeks.

"As anyone with a baby knows, newborns are not too much fun to be around. They sleep, eat, and make you change the diapers. Still, most if not all parents say that having a baby is one of the greatest experiences," said Johannes.

"So, of course, there must be mechanisms which allow for a very strong bond between parents, especially mothers, and the baby. We think that the odour of babies is involved in one of those mechanisms."

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Johannes co-authored a study in 2013 in Frontier Psychology that monitored the brain activity of 30 women when they were exposed to a series of odours. Fifteen had recently given birth, and 15 had never given birth.

When they were exposed to the scent of a two-day-old child's pyjamas, the neural activity increased in the same reward-related areas of the brain that activate when enjoying food, or consuming cocaine.

So a baby is kind of like a class A drug habit. But more expensive, and with less sleep.

What's interesting to note is that although the response was stronger in the new mums, there was a positive reaction in all of the women.

Men's response to that newborn baby smell is not yet understood.

Of course, it's not just their alluring scent that convinces us we should look after babies. They are also designed to be ridiculously cute, with large eyes, chubby cheeks and those cooing sounds they're so good at.

"Infants attract us through all of our senses," said Morten Kringelbach in an Oxford University paper, "which helps make cuteness one of the most basic and powerful forces shaping our behaviour."