B2 中高級 美國腔 373 分類 收藏
Narrator: Lions have them, hippos have them,
and even you and I have them: canines.
Those long, pointy front teeth,
they're actually the longest teeth in the human mouth.
So what are these long, sharp teeth
doing among our short, stubby ones?
Well, contrary to popular belief,
it's not for tearing and ripping meat.
The real reason is actually much more romantic than that.
Human men today have 10% longer canines than women,
and this difference isn't unique to our species.
Our close relatives, gorillas, have
it as well to an even larger extent.
Males' canines are twice as long as females'.
That's because in gorilla society,
males compete for exclusive mating rights to
the entire female troop, and the male
with the longest, most intimidating
set of fangs usually wins.
Over time, gorillas have evolved increasingly longer canines,
but when it comes to humans, our teeth
took a different evolutionary path.
Our canines have actually become shorter over time.
Just look at the canines on the first human,
Ardipithecus ramidus,
or Australopithecus anamensis versus modern humans.
In fact, our canines today are the shortest
they've ever been, and the difference
between male and female canines
got less pronounced as well.
That's because unlike modern gorillas
who take after our shared ancient ancestors,
human men eventually stopped fighting
with their teeth somewhere along the way.
Now, scientists aren't entirely sure why this happened,
but one possibility is that our babies
grew increasingly defenseless, so males
had to spend more time on childcare
and less time on winning a mate.
As a result, all that's left in our mouths today
is the memory of a more slobbery method
of one-upping our peers.
That's right, those canines you carry
around today aren't particularly useful.
For one thing, they're not long enough
to grab and hold on to prey the way lions use them,
and they're not big enough to intimidate
predators' arrivals the way hippos use them.
Instead, they help us bite into food. That's it.
Turns out, evolution isn't always useful,
but while the truth about our canines
might be disappointing, those teeth
are still pretty amazing because
anthropologists use canine size and shape
to help track when humanlike ancestors evolved.
So in a way, our tiny canines make us who we are.


為何人類會有尖尖的犬齒? (The Real Reason Humans Have Those Sharp Front Teeth)

373 分類 收藏
April Lu 發佈於 2019 年 6 月 26 日    gahui yu 翻譯    Evangeline 審核
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