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爪子与指甲 – 译学馆
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爪子与指甲

Claws vs. nails - Matthew Borths

“从一个人的指甲可以了解很多 生活展开时 它们先行”
Consider the claw.
思考一下爪子
Frequently found on four-limbed animals around the world,
世界上很多四肢动物都有爪子
it’s one of nature’s most versatile tools.
爪子是自然界用途最广的工具之一
Bears use claws for digging as well as defense.
熊使用爪子进行挖掘和防御
An eagle’s needle-like talons can pierce the skulls of their prey.
鹰的针状爪子可以刺穿猎物的头骨
And lions can retract their massive claws for easy movement,
狮子可以收起爪子 以方便行动
before flicking them out to hunt.
狩猎时再把爪子伸出来
Even the ancestors of primates
甚至灵长类动物的祖先
used to wield these impressive appendages,
也使用过这些令人印象深刻的附肢
until their claws evolved into nails.
直到后来 它们的爪子演变成了指甲
So what in our evolutionary past
那么在我们的进化史中
led to this manicured adaptation,
导致整齐指甲的适应性进化的是什么
and what can nails do
哪些是指甲能做
that their sharper cousins can’t?
而锋利的爪子却不能做的事?
When nails first appeared in the fossil record around 55.8 million years ago,
约5580万年前 化石中首次出现指甲
claws had already been present for over 260 million years
而哺乳动物和爬行动物的祖先长着爪子的记录
in the ancestors of mammals and reptiles.
已超过2亿6千万年
But despite the gulf of time between their emergence,
尽管它们的出现时间相差甚远
these adaptations are both part of the same evolutionary story.
这些适应性却是同一进化过程的一部分
Both nails and claws are made of keratin—
指甲和爪子都是由角蛋白——
a tough, fibrous protein also found in horns, scales, hooves and hair.
一种坚韧的纤维蛋白组成 还存在于角 鳞片 蹄和头发中
This protein is produced by a wedge of tissue called the keratin matrix.
称为“角蛋白基质”的组织层负责生产这种蛋白质
Rich in blood vessels and nutrients,
该蛋白工厂组织富含血管和营养
this protein factory produces an endless stream of keratin,
生产出源源不断的角蛋白流
which is tightly packed into cells called keratinocytes.
紧紧塞满了角质细胞
These high-density cells
这些高密度的细胞
give nails and claws their trademark toughness.
赋予了指甲和爪子坚韧的特性
Since nails evolved from claws,
因为指甲是由爪子进化而来的
both adaptations produce keratinocytes in the same way.
所以两种适应性都以相同方式产生角质细胞
The cells grow out from the matrix,
细胞从基质中长出来
emerging from the skin where they die and harden into a water-resistant sheath.
露出皮肤就会死亡 然后硬化成防水鞘
The primary difference between the two keratin coverings
两种角质蛋白覆盖物的主要区别
is really just their shape,
实际在于它们的形状
which depends on the shape of the bone at the end of the animal’s digits.
而这取决于动物手指(脚趾)末端的骨骼形状
In claws, the bed of keratinocytes conforms to a narrow finger bone,
爪子是角质细胞顺着狭窄的指骨形成基底
wrapping around the end of the digit and radiating outwards
进而环绕到手指末端 向外辐射
to form a cone-shaped structure.
而形成的一种锥形结构
Animals with nails, on the other hand, have much broader digits,
另一方面 长指甲的动物的手指(脚趾)更宽大
and keratinocytes only cover the top surface of their wide bones.
角质细胞仅覆盖其宽骨的最上面的表面
It’s possible that nails have simply persisted as a side effect
灵长类动物进化出更宽 更灵巧的手指
of primates evolving wider, more dexterous fingers.
指甲可能只是意外的收获
But given what we know about the habitats of our primate ancestors,
但是 据我们对灵长类动物祖先栖息地的了解
it’s more likely that nails came with their own powerful advantages.
指甲很可能具有更强大的优势
High in the forest canopy where these primates lived,
灵长类动物栖息于深林高处
wide finger bones and expansive finger pads were ideal
宽手指骨和宽指垫非常适合
for gripping narrow branches.
抓紧细小的树枝
And nails improved that grip even further.
指甲使其抓得更牢
By providing a rigid surface to press against,
通过可压靠的硬性表面(指甲)
primates could splay out their pads
灵长类动物可以张开指垫
to create even more contact with the trees.
增加与树木的接触面积
Additionally,
此外
nails improved the sensitivity of their digits by providing an extra surface
它们在攀爬时额外表面(指甲)能感知压力变化
to detect changes in pressure while climbing.
从而提高手指的敏感度
This combination of sensitivity and dexterity
灵敏性和灵巧性的结合
gave our ancestors the precise motor control needed to snatch up insects,
为我们的祖先提供了精确的运动控制能力
pinch berries and seeds, and keep a firm grip on slim branches.
可以捉住昆虫 捏住果酱和种子 牢牢抓住纤细的树枝
The evolution of nails and the evolution of opposable thumbs and toes
指甲的进化与可对捏的拇指和脚趾的进化
are closely linked.
密切相关
And when our ancestors moved down from the trees,
当我们的祖先从树上搬迁到陆地生活时
this flexible grasp enabled them to create and wield complex tools.
这种灵活的抓握能力使它们能制造并使用复杂工具
Even if it was possible for wide fingers to sport claws,
即使宽手指也可以掌控爪子
their sharp points would’ve likely interfered
但尖锐的爪尖可能会干扰
with these primates’ regular tasks.
这些灵长类动物的日常工作
Claws are ideal for piercing, puncturing, and hooking,
爪子适用于穿透 刺破和钩住东西
but their points make grabbing difficult, and potentially dangerous.
但爪尖使抓取困难 并且有潜在危险
However, both claws and nails are used in some unexpected ways.
但是爪子和指甲都有意想不到的使用方式
Manatees use nails to grasp their food,
海牛用指甲抓住食物
and researchers think elephant toenails may sense vibrations
研究人员认为大象的脚趾甲或许能感知地面震动
in the ground to help them hear.
以帮助它们听见远处的声音
Meanwhile, some primates, like the aye-ayes of Madagascar,
同时 一些灵长类动物 如马达加斯加指猴
have re-acquired claws.
有再生爪子的能力
They use these extra-long appendages to tap branches and trunks,
它们用这些长长的爪子敲打树枝和树干的同时
while listening for hollow sections with their bat-like ears.
用蝙蝠状耳朵倾听 以寻找空心部位
When they hear an opening, they burrow into the tree
当它们听到空响时 就用爪子挖开 并深入树中
and skewer grubs with their needle-like middle finger.
然后用针状中指把幼虫串起来
We’ve only scratched the surface of all the incredible ways nails and claws
关于动物界令人不可思议的指甲和爪子的使用方式
are used throughout the animal kingdom.
我们本次只做了初步了解
But as for which of these adaptations is better?
至于这些适应性中的哪一种更好
That’s an answer we may never nail down.
我们可能永远无从知晓

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视频概述

爪子和指甲有什么区别?哪个更有用?

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视频来源

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