(My niece, husband and mum)
I wondered this when my eldest daughter was a baby 22 years ago, and have pondered on this thought with every baby I have raised.
My theory is that we haven't evolved significantly in thousands of years. Our babies don't know they are born into a modern nuclear family, with a modern busy lifestyle, where support isn't as it was for our ancestors. Our babies aren't born evolved with this knowledge.
Our babies today are still born with the same instincts as our ancestors.
We likely feed more at night as that was when our ancestors would have perhaps been safest, because they were settling down, huddled together, protected by fire and safety of numbers. By day our hunter gatherer ancestors would have have been busy, often walking many miles in some cases. So our hormones evolved to fit this pattern of living too.
Think about the fact we were mobile hunter gatherers for around 350000 years, and only living as farming communities for roughly 11000 years.
A book my husband,who is an archaeologist, showed me, suggests to look at our evolution for better living.
"For the last three million years or more, we evolved as hunter'gatherers, living of the land in small tribal societies, developing a working relationship with nature. Culturally society is changing exponentially. Anatomically,however our genetic evolution is rather slower." (2)
Therefore our babies instinctual patterns haven't evolved to fit modern living.
At night we produce a higher amount of prolactin which is the hormone that maintains breast feeding.
Studies have shown that prolactin release follows a circadian rhythm, with highest levels of secretion at night and in the morning.(1)
If we don't feed at night we are likely to have reduced milk supply within a matter of weeks because we have reduced prolactin levels.
It's all naturally evolved to fit how our ancestors lived before sedentism and agriculture.
If we put our baby down alone they would fear predators, or being left behind, although they don't know what a predator is their instincts and hormones are still created to fit our ancestral hunter gatherer way of living.
So next time your baby won't be put down know it's not them being difficult, or 'wrapping you around their finger', as I've heard people say. It is just their built in self protection for survival.
2) Milne, G. (2015). The Evolutionary Determinants of Health Programme: Urban Living in the 21st Century from a Human Evolutionary Perspective. Archaeology International, 18(0), p.84.
*I'd like also to mention an amazing book that inspired my thoughts on this dubject by Professor Robert Winston on why babies do things they do, and subjects like why their eyes are blue, written in 1990's of which I sadly can't recall the title and haven't found again for 22 years