As mentioned previously, the traits that animals gained through evolution can be messy. Sometimes, they work against each other.
Don’t you sometimes envy a gnu? When the gnu cow has her calf, it will be standing and ready to walk within an hour! But our human babies need months until they even attempt to get up. So we applaud when they start holding up their little heads or turning on their bellies.
We’re right to celebrate this! Our species has evolved to have a more complex brain than our ancestors and also to walk upright. These are two key factors that caused our babies to be so dependent at birth and the years that follow because:
- A larger brain meant a bigger head
- Walking upright meant our legs couldn’t be so far apart
Therefore the baby’s big head has less space to go through the birth canal. That could cause both the baby and the mother to die at childbirth.
So how come our ancestors didn’t die out because of this?
Because some females had their babies prematurely, which means these children were born smaller and their heads were more malleable. That increased the chances of mother and baby surviving the birth. Over time, females that delivered premature babies were the ones that survived – and their children too.
Today, we don’t consider a baby born after a 9-month gestation to be premature and we’re used to the fact that we need to care for our infants for a long, long time, since they still have to develop in so many ways.
Being sociable also helped our ancestors to survive: with this more difficult birth and the dependent baby, having a community that supports its members really increased the chances of survival of mothers and babies.
This is just one set of changes that happened over our evolution that lead to us becoming the way we are today. All living beings went through millions of years of tiny changes and there are lots of amazing stories about those as well.
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| Video: A brief history of Humankind – Lesson 01 part 3 History professor Yuval Noah Harari gave this course some years ago, I recommend all lessons. This specific lesson is the one that talks about the relationship of our babies being born ‘half-baked’ due to large brains and bipedalism. I’ve set the video to start at the moment he starts talking about this, but the beginning is also very recommendable |
| Article from the Smithsonian Musem: Brains Article with images of how the size of the human brain increased over the millenia |