There may be a counterintuitive origin to human intelligence

Flickr/Oleg Sidorenko

There is possibly nothing more helpless (and adorable) as a newborn baby.

In that first year or so, they are reliant on others for everything from food to movement.

This makes humans pretty unique among other animals in the animal kingdom.

A new study looks at why that might be the case. It suggested that the connection between parent and dependent child may have allowed us to develop intelligence more rapidly than other animals.

For their study, published Monday in the journal Proceedings of the National Academy of Sciences, researchers at the University of Rochester designed a model to evaluate the relationship among three things: the brain size at birth of babies across populations, their birth month, and how long the child survived.

Their idea? The reason humans became so smart beyond needing to survive and reproduce was influenced by our need to take care of our little ones, something called a "positive evolutionary feedback loop."

Here's how that loop works: Human babies are born unusually early in their brain development (for example, to get to the same cognitive state as a chimpanzee baby, humans would have to hang out for 18-21 months in the womb). There are a few theories as to why that happens, but regardless, this makes for some pretty helpless babies who still have a lot of brain developing to do.

And taking care of these babies isn't easy. It requires more intelligent parents with larger brains, the researchers suggested. To reach their conclusion, the researchers looked in particular at when children were weaned as well as other factors like to infant mortality rates and their connection to mother's education levels.

"Our modeling has shown that the evolutionary dynamics of caring for [newborns] may select for intelligence, which in turn requires even more brainpower, pushing infants to be born even earlier to accommodate their larger brains," the researchers wrote in their study.

The researchers acknowledge that it doesn't give the full evolutionary picture, but rather focuses just on a simplified facet of it. 

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