Hey Smart People,
The first thing a baby giraffe experiences after being born is a 2 meter fall straight
down to the ground.
But within an hour, it’s standing, walking, and nursing on its own.
And a blue whale calf, after nearly a year growing inside mom, can swim to the surface
moments after being born.
Human babies on the other hand?
We’re born unable to move or eat on our own, we can’t communicate or fully sense
our world, and we leak Everywhere.
If humans are so smart, why are our babies so… un-smart?
Human babies begin life so undeveloped, that many people refer to a baby’s first few
months of life as the fourth trimester.
Compared to other animals, we lie on the “altricial” end of the spectrum.
Compare that with, say, a baby cow, a precocial animal, whose brain and body is developed
enough that they can stand and run just moments after being born.
Tiny humans require a ton of parental care before we’re ready to be on our own.
Our parents not only grow us for 9 months or so, they carry us, they feed us, they keep
us from dying, and teach us how to provide for ourselves for 15, 18 years… heck these
days even over 30 isn’t unheard of.
It’s actually totally normal.
That’s because, well, our brains come out half-cooked at best.
When we’re born our brain is around 30% the size of our adult brain.
That’s the smallest of all of our primate relatives.
Why does our smart species have such small-brained babies?
For a long time, scientists’ best answer to that question was the obstetric dilemma.
Basically, our brains come out as big as they physically can be.
The obstetric dilemma goes like this: if our brains were any bigger at birth, they wouldn’t
fit out the birth canal.
And if female pelvises were any wider, they would make walking and running less efficient…
which might not affect your life that much, but would’ve made it easier for our ancestors
to become dinner… which means no babies, which means no you or me.
So here, natural selection found a compromise: mom’s pelvis stays narrow enough to walk
and run, and babies are born earlier so their noggins don’t get stuck.
It’s a pretty logical idea.
But it doesn’t hold water.
Male and female bodies do have significant anatomical differences, but research has found
that wider or roomier pelvises don’t make walking and running, AKA “locomotion”
less efficient.
And, some women already have pelvic openings wide enough to fit bigger heads and brains.
Not every woman does, but if there was strong pressure from natural selection for roomier
pelvises, they’d have become more common.
So pelvis size isn’t why our babies come out half-baked.
The real answer might have more to do with metabolism.
The bigger a developing baby gets, the more it demands from mom.
I mean, women grow a completely new organ, the placenta, not to mention a complete humanbeing, inside their bodies, and that takes energy!
It might be that mom’s ability to provide enough energy for growing baby determines
when baby is born.
Humans and all other animals have what’s called a basal metabolic rate.
It’s how much energy we burn when we’re not doing anything else.
A Tour de France cyclist at peak human performance can hit maybe four or five times their basemetabolism.
But most of us normal humans?
We max out at around two times our basal rate.
We just can’t run our biological engines any higher for very long.
Like overclocking a CPU, there’s just a physical limit to how much extra energy we
can create.
For the last third of pregnancy, and even into nursing, a mother is at the limit, burning
twice as much energy as before baby.
Nine months happens to be right about the time a growing baby starts to demand more
energy than mom can provide, so it’s born.
It’s called the EGG hypothesis, or “Energetics of Gestation and Fetal Growth”.
But I like egg.
But even energy and metabolism might not be the full answer.
It could be that how helpless our babies are when they are born has had a big influence
on what happens after they are born.
How self-sufficient an animal’s young are at birth can be determined by a lot of things.
If they have to run from predators, if their parents are quickly on the move, or if their
egg had enough nutrients to hatch big.
But having helpless babies, and helping them get smarter, might’ve forced ancient human
parents to get smarter too.
It’s a pretty cool theory.
It works like this:
When we look at human ancestors, it’s clear that natural selection favored humans with
larger brains, because they tended to be smarter.
But human babies’ brains are already born as big as they can be because of the whole
energy thing, so the only way to make a bigger brain is for the brain to spend more time
growing after you’re born.
That requires longer parental care, which requires more intelligent parents, which over
time selects for parents with bigger brains.
It’s a feedback loop.
The more intelligent the parents, the better and longer they can care for a helpless baby,
and the bigger the baby’s brain can eventually grow.
Research tells us that modern human brains don’t finish developing until about age
25, which means I have been past my peak for a while, but it supports this idea that intelligent
parents caring for their children for longer have helped extend the amount of time our
brains get to grow before they’re done.
More intelligence probably made early human ancestors more social too, which made raising
helpless young even easier, which would start a whole other feedback loop making us more
and more social over time.
These aren’t the kinds of things that you’d notice in a generation or two.
They’d evolve across hundreds of generations.
There are definitely other reasons that our ancestors’ brains grew.
Making tools and hunting animals?
That helped a lot.
Harnessing fire and cooking food to get more calories and nutrients helped too.
But ask any parent: It is not easy to raise a helpless baby, especially for a decade or
two like humans do.
It takes our unique intelligence, and our unique social abilities to do it.
I mean, you give a human baby to a group of chimpanzees, it’s not gonna end well.
In the end, like all interesting and complex human traits, our extreme intelligence and
our babies’ relative lack thereof can’t be explained by just one reason.
It’s a mix of many reasons.
Having a baby is not an easy thing to do.
But the very fact that humans are so good at having more humans, and caring for them
and each other as deeply and for as long as we do, is proof enough that we are a very
special species indeed.
Stay curious.
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