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Proof of evolution on your body.

Your body is a temple,

temple - храм

but it’s also a museum of natural history.

Look closely and you’ll see parts that aren’t there because you need them

but because your animal ancestors did.

ancestor - предок, прародитель

No longer serving their previous function

to service - обслуживать

but not costly enough to have disappeared.

costly - дорогой, ценный (to cost - стоить)

These remnants of our deep history

remnant - остаток, пережиток

only make sense within the framework of evolution by natural selection.

framework - рамки, структура, основа, каркас

With your arm on a flat surface,

flat - плоский
surface - поверхность

push your thumb against your pinky

thumb - большой палец
pinky - мизинец

and tip your hand slightly up.

to tip - наклонить
slightly - слегка

If you see a raised band in the middle of the wrist,

band - связка
wrist - запястье

you’ve got a vestigial muscle in your forearm.

vestigial - рудиментарный, остаточный, исчезающий
forearm - предплечье

That tendon you see connects to the palmaris longus,

tendon - сухожилие
palmaris longus - длинная ладонная мышца

a muscle that around 10-15% of people

are missing on one or both of their arms.

It doesn’t make them any weaker though.

There’s no difference in grip strength.

grip - хватка, зажим, захват

In fact, it’s one of the first tendons that surgeons will take out

surgeon - хирург

so they can use it in reconstructive and cosmetic surgeries.

You can find the palmaris longus across mammal species,

mammal - млекопетающее

but it’s most developed among those that use their forelimbs to move around.

forelimb - передняя конечность

In primates, that means the muscle is longer in lemurs and monkeys

and shorter in chimps, gorillas, and other apes

that don’t do a lot of scrambling through trees.

to scramble - карабкаться, бороться

It’s not the only leftover muscle that we've got.

leftover - остаточный (a leftover - остаток, пережиток)

Look at the three that are attached to our outer ear.

attached - прикрепленный, приложенный

We can’t get much movement out of these muscles,

especially compared to some of our mammal relatives

compared to - по сравнению с
relatives - родственники

who use them to locate the sources of sounds.

source - источник

Presumably this would have been quite helpful for early nocturnal mammals.

presumably - предположительно
nocturnal - ночной образ жизни

In humans, you can still detect the remnants of this adaptation with electrodes.

electrode - электрод

In one study researchers recorded a spike of activity

spike - шип, острие, колос

in the ear muscle cells in response to a sudden sound.

response - ответ, реакция, отклик
sudden - внезапный, неожиданный

Not enough to move the ear, but detectable.

detectable - обнаруживаемый

And you can probably guess the location of the sound based on the results

- it came from a speaker placed to the left of the study subjects.

So this is their left ear subconsciously trying (and failing)

subconsciously - подсознательно

to pivot toward the sound.

to pivot - повернуть(ся), вертеться

You can see another futile effort by our vestigial body parts

futile - бесполезный, пустой, тщетный

when you get goosebumps.

When we’re cold, tiny muscles attached to our body hairs contract,

pulling the hair upright

which causes the surrounding skin to form a bump.

bump - удар, шишка, выпуклость, столкновение

For our furry mammal relatives,

furry - пушистый, меховой (fur - мех)

the raised hair increases the amount of space for insulation,

to raise - поднимать
insulation - изоляция

helping them stay warm.

Birds can do this too.

You’ve probably seen a puffy pigeon on a cold day.

puffy - опухший, пухлый, пышный, надутый

Adrenaline is one of the hormones involved

in the body’s response to cold temperatures,

and it’s also part of the fight or flight response.

So it helps some animals appear larger when they’re threatened.

And it may be why surprising and emotional turns in music

can give some people goosebumps.

And then there’s our tail.

At the end of our spine are a set of fused vertebrae.

to fuse - сливаться, сплавлять
vertebrae - позвонки (vertebra - позвонок)

Some people have 3, some have 5.

We call it the tailbone.

tailbone - копчик

It now serves as an anchor for some pelvic muscles

pelvic - тазовый

but it’s also what’s left of our ancestors’ tails.

Every one of us actually had a tail at one point.

When the basic body plan is being laid out

at around 4 weeks of gestation,

humans embryos closely resemble embryos of other vertebrates.

to resemble - походить, иметь сходство, быть похожим

And that includes a tail

with 10-12 developing vertebrae.

In many other animals it continues to develop into a proper tail.

But in humans and other apes,

the cells in the tail are programmed to die

a few weeks after they appear.

to appear - появляться

Very rarely though,

a mutation allows the ancestral blueprint to prevail

ancestral - родовой, наследственный
to blueprint - план, проект, светокопия, программа, калька
to prevail - преобладать, превалировать, возобладать, господствовать

and a human baby will be born with a true vestigial tail.

The most adorable vestigial behavior is the palmar grasp reflex,

palmar - ладонный (palm - ладонь, пальма)
to grasp - понять, осознать; схватить, усвоить

where infants up until they’re about 6 months old

infant - младенец

have this incredible grasp on whatever you put in their hand.

There’s a similar reflex for their feet.

I wanted to show you this great piece of footage from the 1930s

footage - кадры

where they demonstrated this behavior.

These babies are only 1 month old

and you can see that their inner monkey

can support their entire weight.

entire - весь, целый, полный