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

仔細觀看，你會發現有些毫無用處的身體部位

but because your animal ancestors did. No longer serving their previous function

是因應動物祖先的需求而存在。雖然這些部位跟以往的功能不同

but not costly enough to have disappeared, these remnants of our deep history only make

但也不至於完全消失，我們深厚歷史下的這些遺跡

sense within the framework of evolution by natural selection.

在物競天擇的進化論下有跡可循

With your arm on a flat surface, push your thumb against your pinky and tip your hand slightly up.

將手臂平放、拇指和小指互碰，並輕輕將手掌向上提起

If you see a raised band in the middle of the wrist, you’ve got a vestigial muscle in your forearm.

若你手腕中間有個鼓起的筋，那是在你前臂上留下來的一塊肌肉

That tendon you see connects to the palmaris longus,

你看到的這根筋就是掌長肌

a muscle that around 10-15% of people are missing on one or both of their arms.

約莫 10%-15%的人沒有這條肌肉，有些人只有其中一隻手臂有，有些人是兩隻手臂都沒有

It doesn’t make them any weaker though. There’s no difference in grip strength.

但是失去掌長肌的人並沒有比較脆弱，他們的手掌握力與一般人相同

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

事實上，這是外科手術中最先取出利用的肌腱之一，可用在

in reconstructive and cosmetic surgeries. You can find the palmaris longus across mammal species,

重建和美容手術中。 哺乳動物身上也有掌長肌

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

而其中，靠前肢移動的動物此肌肉最為發達

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

在靈長類動物裡，狐猴和猿猴的掌長肌比較長，而在黑猩猩屬、

gorillas, and other apes that don’t do a lot of scrambling through trees.

大猩猩和那些不需經常在樹中攀爬的物種則較短

It’s not the only leftover muscle that we've got. Look at the three that are attached to our outer ear.

它並不是唯一一個殘留在我們身體的肌肉，看這三塊在我們耳朵外側的肌肉

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

這些肌肉的行動範圍相當有限

especially compared to some of our mammal relatives who use them to locate the sources of sounds.

特別是相較於親哺乳動物，他們用這些肌肉來定位聲源

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

這或許對早期夜間哺乳動物相當實用

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

對人類來說，你仍然可以利用電極觀測到這塊肌肉的演變

In one study researchers recorded a spike of activity in the ear muscle cells

在某研究中，研究人員針對耳朵肌肉對

in response to a sudden sound. Not enough to move the ear,

突發聲響的活動，其回應並為讓耳朵移動

but detectable. And you can probably guess the location of

但是可偵測到的。根據這個結果，你大概能猜出

the sound based on the results - it came from a speaker to the left of the study subjects.

這個聲音的來源，他來自研究對象的左測

So this is their left ear subconsciously trying and failing to pivot toward the sound.

因此他們的左耳潛意識地想向聲音處移動

You can see another futile effort by our vestigial body parts when you get goosebumps.

雞皮疙瘩是我們身體演化證據的另外一環

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

當我們受寒，附著在我們汗毛上的肌肉會收縮，

upright which causes the surrounding skin to form a bump.

讓汗毛豎起來，並使周圍的皮膚隆起

For our furry mammal relatives, the raised hair increases the amount of space for insulation,

對我們毛茸茸的哺乳動物近親，這些隆起的毛髮可以增加絕緣的空間

helping them stay warm. Birds can do this too. you’ve probably seen

幫助他們保暖。鳥類也可以這麼做，你或許看過

a puffy pigeon on a cold day. Adrenaline is one of the hormones involved

在寒冬時身體澎起的鴿子。腎上腺素讓

in the body’s response to cold temperatures, and it’s also part of the fight or flight response.

我們的身體對低溫有所反應，它也是我們於「戰鬥或逃跑」反應時所需的賀爾蒙。

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

它亦讓某些動物在飽受威脅時身體膨大。

And it may be why surprising and emotional

這可能就是令人吃驚或感動的音樂

turns in music can give some people goosebumps. And then there’s our tail. At the end of

能使人起雞皮疙瘩的原因。來談談我們的尾巴！

our spine are a set of fused vertebrae - some people have 3, some have 5. We call it the tailbone.

我們的脊髓的末端有一組融合椎，有些人有三個、或五個，我們稱之為尾骨

It now serves as an anchor for some pelvic muscles

它現在作為骨盆肌肉的支架

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

它也是我們祖先尾巴留下來的

Every one of us actually had a tail at one point. When the basic body plan is being laid

每個人其實都曾有過尾巴。在母體內孕育

out at around 4 weeks of gestation, humans embryos closely resemble embryos of other vertebrates.

妊娠期四周的時候，人類胚胎和其他脊椎動物很相似

And that includes a tail with 10-12 developing vertebrae.

這包括一個尾巴，其中含有10到12個成長中的脊椎骨

In many other animals it continues to develop

在許多其他動物中，它繼續成長為

into a proper tail. But in humans and other apes, the cells in

一個真尾巴。但是人類和其他人猿類的尾細胞

the tail are programmed to die a few weeks after they appear.

會在出現的幾週後死去。

Vary rarely though, a mutation allows the ancestral blueprint to prevail and a human

雖然非常罕見，但是基因突變能讓祖先基因捲土重來

baby will be born with a true vestigial tail.

並使小嬰兒出生時也有著 (因器官萎縮) 尾巴。

The most adorable vestigial behavior is the palmar grasp reflex,

最迷人的演化部位是手掌抓握反射

where infants up until they’re about 6 months old have this incredible

嬰兒一直到6個月大時都還有這項不可置信的抓握能力

grasp on whatever you put in their hand. There’s a similar reflex for their feet. I wanted

不論你在他們手中放什麼。他們的腳也有相似的反射，我想

to show you this great piece of footage from the 1930s where they demonstrated this behavior.

給你們看看這項神奇的行為，1930年他們證明了這個行為

These babies are only 1 month old and you can see that their inner monkey can support their entire weight.

這些小孩僅僅一個月大，而手臂的力量卻能夠承受他們全身的重量，彷彿喚醒了內在小猴子