Name: なぜ人間はほとんどの動物よりも遅いのか？ (Why Are Humans Slower Than Most Animals?)
Uploaded: 2021-01-14T06:47:44.000Z
Duration: 3 min 56 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

People tell me I’m slow. Yeah well, you’re slow. Everybody’s slow. We’re all slow.

If you’ve ever raced a cheetah and you’re not named Usain Bolt, you probably lost. Or

heck if you even tried racing against your cat, I bet you still lost. From horses, to

dogs, to birds, it seems the entire animal kingdom is faster and stronger than we are.

Why? Well we evolved to fit into our own ecological niche. But even compared to our nearest relatives,

the chimpanzee and bonobos, we are considerably weaker. We weren’t always this way. According

to Dan Lieberman, a biological anthropologist at Harvard University, our “chimp-like ancestor

was like a power athlete that was much stronger and faster than humans, but they had no endurance."

But we traded our brawn for bigger brains and the ability to outrun our prey in a long

When our ancestors evolved from being mostly tree dwellers to savannah walkers, they probably

traded strength and speed for endurance. This is creatively called the endurance hypothesis.

Some researchers believe that humans evolved a unique predatory style. Rather than a fast

and furious chase, like a cheetah or Vin Diesel, humans take the slow and steady, wear-down-your-prey-till-it-collapses-from-exhaustion

kind of action. And this takes very specific types of muscles. By comparison, cheetahs

have muscles that are tailored to reacting quickly so they can reach top speed of around

70 miles per hour. But the tradeoff is they get exhausted quickly, they have no endurance.

While we can never run that fast, we can run for a long time, maybe longer than any other

animal. Sure less exciting than a high speed chase, but incredibly effective.

But you’re also slow because you’re weak! Don’t feel bad, we all are, comparatively

speaking. One of our closest relatives, the chimpanzee is about twice as strong as a human.

Because they’re arboreal and spend most of their time in trees, most of their strength

Our ancestors probably had similar muscle strength to a chimpanzee around six million

years ago according to a study published in PLOS One. The researchers found that in the

few million years since, human beings evolved dramatically. Our brains got bigger, specifically

in our prefrontal cortex, the part that deals with long term goal planning. They found that

the prefrontal cortex was RADICALLY different in humans from that in chimpanzees, monkeys,

and mice. It seemed to have evolved 4 times faster than the other parts of the body. And

that’s because in part, humans started to evolve social structures that allowed us to,

say, work together as a team to take down bigger prey.

But there is a downside to a bigger brain. A bigger brain consumes more energy. Our brains

consume 20% of the energy we use, which is a lot compared to other animals. So where

did the energy come from? Maybe from our muscles.

The researchers also found our ancestor’s MUSCLES changed rapidly too. Very rapidly,

about 8 times faster than the rest of our body. So researchers believe that to deal

with the energy demands of a bigger brain, our ancestors evolved smaller muscles to compensate.

You may think this contradicts the Darwinian principle of “survival of the fittest,”

but “fit” in this context doesn’t mean physical fitness. It means an organism fits

in a niche long enough to reproduce, so the genetic lineage survives. And it’s not that

being a smart wimp is always better than being a big dumb ox or vice versa, it’s a matter

of what’s most beneficial for an organism based on its environment and competition.

If coming down from the trees and learning to make fire means one day your offspring

will populate the globe, it’s probably worth giving up looking like a species of Mr. Universes.

CTA video So you can’t outrun a cheetah but you can

definitely out-walk it. Julia covers the endurance hypothesis in more detail here.

If you had the option to be ripped but also couldn’t form basic sentences, would you

take it? Mash your keyboard in the comments, subscribe

for more, and I’ll see you next time on DNews.