Why do we have crooked teeth when our ancestors didn’t? - G. Richard Scott
All these ancient skulls have
perfectly straight teeth,
despite almost certainly
never sporting braces.
And this isn't some strange sample.
According to the fossil record,
ancient humans usually had straight teeth,
complete with third molars—
or wisdom teeth.
In fact, the dental dilemmas
that fuel the demand for braces
and wisdom teeth extractions today
appear to be recent developments.
So what happened?
While it’s nearly impossible
to know for sure,
scientists have a hypothesis.
A couple million years ago,
the ancestors of modern humans lived
a subsistence lifestyle.
Their teeth and jaws had to work hard
to make the food they ate digestible.
Indeed, the surfaces of many of their
teeth show extensive wear and flattening.
They also had larger jaws
and teeth overall.
At some point, they began using tools
and fire to cook and prepare food,
which helped break it down.
A lot more time passed and,
around 12,000 years ago,
some humans started farming
and domesticating animals and plants.
Over the course of several thousand years,
it became more common for people
to process and refine their food.
Milling technologies helped remove
the tougher parts of grains,
like the germ and bran
from rice and wheat.
Fast forward to the industrial Revolution,
and technological innovations dramatically
accelerated these processes.
In a relatively short time,
many human mouths were relieved
of a great deal
of their grinding, crushing,
and pulverizing duties.
And interestingly, it was around this time
that tooth crookedness
appears to have become more common.
Examining fossils
spanning millions of years of evolution,
researchers have observed
a gradual decrease in tooth and jaw size
in humans and our ancestors.
Many think that,
for most of human history,
dietary shifts— like the introduction
of meat and the advent of cooking—
were gradual,
and that changes in tooth and jaw size
basically kept pace with one another.
But with the more recent revolutions
in agricultural and culinary habits,
that relationship changed.
As the theory goes,
over a relatively short period,
some human populations saw
a decrease in jawbone size,
while teeth stayed roughly the same size,
meaning they're left vying
for limited space.
When they do grow in,
they may displace others
and get jostled into some
eccentric positions.
And then wisdom teeth, which are usually
the last to make their debut,
seem to only complicate things further.
In many cases, they have little
or no space to emerge.
This can lead to impacted wisdom teeth,
which may cause discomfort and infections
if not surgically removed.
So larger jaws appear to be associated
with greater chewing demands.
And many scientists think that as people's
diets have become less chewy,
their jaws have gotten smaller—
and that this has led to dental crowding,
resulting in dental crookedness
and impacted wisdom teeth.
This hypothesis has been supported
by some preliminary experimental data.
In a 1983 study, researchers
raised 43 squirrel monkeys
on diets of either naturally tough
or artificially soft food.
Those fed softer food had
more crowded premolars,
rotated or displaced teeth,
and narrower dental arches.
And a 2004 study similarly observed
that hyraxes raised on cooked foods
experienced roughly 10% less growth
in facial areas involved in chewing
compared to those given raw
and dried foods.
In other words, the issue at large
seems to be environmental—
or one of lifestyle—
instead of a genetic one,
though heritable factors may be at play
in some instances.
It’s estimated that somewhere
between 30 to 60% of people today
experience some level of tooth crowding.
But this trend varies
across global populations.
Some people naturally
never have wisdom teeth.
And some don’t experience
tooth crowding or crookedness
and still get their wisdom teeth
without a hitch.
This seems to coincide with diets
that are less processed.
So how can we prevent
tooth crowding early,
using lifestyle changes and orthodontics?
Well, it’s certainly
something to chew over.
