“牛奶是给婴儿喝的”——阿诺德·施瓦辛格
The Tibetan high plateau lies about 4500 meters above sea level,
在海拔约4500米高的青藏高原上
with only 60% of the oxygen found below.
氧气含量只有平原上的60%
While visitors and recent settlers struggle with altitude sickness,
当游客和新来的定居者饱受高原反应困扰时
native Tibetans sprint up mountains.
当地的西藏人却可以飞奔上山
This ability comes not from training or practice,
这种能力不是通过训练或练习得来的
but from changes to a few genes
而是源自一些基因变异
that allow their bodies to make the most of limited oxygen.
这些变异让身体可以充分利用有限的氧气
These differences are apparent from birth.
这种差异从出生起就显而易见了
Tibetan babies have, on average, higher birth weights,
藏族的婴儿出生时平均体重更重
higher oxygen saturation,
血氧饱和度也更高
and are much likelier to survive than other babies born in this environment.
比在这样的环境中出生的其他婴儿更易存活
These genetic changes are estimated to have evolved
据估计 这些基因的变化是经过
over the last 3,000 years or so, and are ongoing.
约3000年的进化形成的 且仍在持续
That may sound like a long time,
3000年听起来很长
but would be the fastest an adaptation has ever evolved in a human population.
但在人类所有适应性进化中是最快的
It’s clear that human evolution isn’t over,
显然 人类进化从未停止
so what are other recent changes?
那近来有哪些其他变化呢？
And will our technological and scientific innovations impact our evolution?
技术和科学的革新会影响人类的进化吗？
In the past few thousand years,
在过去的几千年中
many populations have evolved genetic adaptations to their local environments.
很多人类族群进化出了适应当地环境的基因
People in Siberia and the high arctic are uniquely adapted
西伯利亚和北极地区的人们具有独特的适应能力
to survive extreme cold.
能够在极寒环境中生存
They’re slower to develop frostbite,
他们比大多数人更不易长冻疮
and can continue to use their hands in subzero temperatures
同时在零下温度中 能用手劳作的时间
much longer than most people.
也比大多数人长得多
They’ve undergone selection for a higher metabolic rate
他们经过自然选择 有了更高的新陈代谢率
that increases heat production.
能产生更多的热量
Further south, the Bajau people of southeast Asia can dive 70 meters
而在南边 东南亚的巴瑶人可以潜入70米深水
and stay underwater for almost fifteen minutes.
并在水下待上大概15分钟
Over thousands of years living as nomadic hunters at sea,
作为在海上生活了几千年的“游牧民族”
they have genetically-hardwired unusually large spleens
他们生来就有不同寻常的大号脾脏
that act as oxygen stores, enabling them to stay underwater for longer—
用以储存氧气 使他们能在水下待上更久
an adaptation similar to that of deep diving seals.
就像深潜海豹的遗传适应一样
Though it may seem pedestrian by comparison,
虽然和前面提到的进化比起来平平无奇
the ability to drink milk is another such adaptation.
但喝奶的能力也是一种适应
All mammals can drink their mother’s milk as babies.
所有哺乳动物在婴儿时期都会喝母乳
After weaning they switch off the gene that allows them to digest milk.
断奶后 他们就会关闭消化奶类的基因
But communities in sub-Saharan Africa, the middle east and northwest Europe
但在撒哈拉以南的非洲 中东和欧洲西北部
that used cows for milk have seen a rapid increase in DNA variants
在过去的七八千年中 养牛饮奶的族群中
that prevent the gene from switching off over the last 7 to 8 thousand years.
阻止奶类消化基因关闭的DNA变体出现了激增
At least in Europe, milk drinking may have given people a source of calcium
至少在欧洲 人们往北迁徙时
to aid in vitamin D production, as they moved north,
作为维生素D的主要来源的阳光会减少
and sunlight, the usual source of vitamin D, decreased.
于是人们喝奶来获取钙 帮助吸收维生素D
Though not always in obvious ways,
虽然变化并不都很明显
all of these changes improve people’s chance of surviving to reproductive age.
但这些变化都提高了人们活到生育年龄的概率
That’s what drives natural selection,
那是驱动着自然选择的力量
the force behind all these evolutionary changes.
是在背后推动着所有进化的力量
Modern medicine removes many of these selective pressures
我们的基因有时遇上传染病 可能会致死
by keeping us alive when our genes,
现代医学却让我们得以存活
sometimes combined with infectious diseases, would have killed us.
从而消除了许多自然选择的压力
Antibiotics, vaccines, clean water and good sanitation
抗生素 疫苗 净水以及良好的卫生环境
all make differences between our genes less important.
都会让基因上的不同变得没那么重要
Similarly, our ability to cure childhood cancers,
同样地 我们治疗儿童癌症的能力
surgically extract inflamed appendixes,
手术切除发炎阑尾的能力
and deliver babies whose mothers have life-threatening
以及为患有危及生命的特定妊娠疾病的母亲
pregnancy-specific conditions,
接生孩子的能力
all tend to stop selection by allowing more people to survive
都有助于让更多的人活到生育年龄
to a reproductive age.
从而阻止自然选择
But even if every person on Earth has access to modern medicine,
但即使地球上每个人都能享受现代医疗
it won’t spell the end of human evolution.
也并不意味着人类的进化的终止
That’s because there are other aspects of evolution besides natural selection.
因为除了自然选择 还有其他进化的因素
Modern medicine makes genetic variation that would have been subject to natural selection
现代医学让遗传变异从原本的顺应自然选择
subject to what’s called genetic drift instead.
向所谓的遗传漂变转变
With genetic drift, genetic differences vary randomly within a population.
遗传漂变让族群中的基因差异随机地变化
On a genetic level, modern medicine might actually increase variety,
从遗传学角度来说 现代医学会提升基因多样性
because harmful mutations don’t kill people and thus aren’t eliminated.
因为有害的基因突变不再致死 所以也不会消失
This variation doesn’t necessarily translate
不过 这种变异并不一定会转变成
to observable, or phenotypic differences among people, however.
人群中的的可见或表型差异
Researchers have also been investigating
研究者们也正在探究
whether genetic adaptations to a specific environment
特定环境下快速产生的遗传适应
could appear very quickly through epigenetic modifacation:
是否与表观遗传修饰有关
changes not to genes themselves,
即：改变的不是基因本身
but to whether and when certain genes are expressed.
而是特定的基因 是否或何时表达
These changes can happen during a lifetime,
遗传适应的变化在人的一生中都能发生
and may even be passed to offspring.
甚至可能传给后代
But so far researchers are conflicted
但迄今为止 研究者仍在争论
over whether epigenetic modifications
表观遗传修饰造成的变化
can really persist over many generations
是否可以传给许多代人
and lead to lasting changes in populations.
并导致人口的长期变化
There may also be other contributors to human evolution.
此外 可能也有其他因素影响着人类进化
Modern medicine and technology are very new,
即使和自然选择造成的最快 最近的变化相比
even compared to the quickest, most recent changes by natural selection.
现代医学和技术的历史也是新兴事物
So only time can tell how our present will shape our future.
所以 只有时间能告诉我们 现在会如何影响未来
Earth is 4.5 billion years old.
地球已经四十五亿岁了
How did humans come to define it in such a tiny fraction of that time?
人类是如何在这么短的时间内确定这一点的呢？
It’s what makes us brilliant the same thing that makes us deadly.
这既是让我们拥有智慧的东西 也是致命的东西
Explore our place in the universe with sapiens.
用智慧探索人类在宇宙中的位置
Download a free audio book version from audible.com/ted-ed.
从audiences.com/ted-ed下载免费的有声书版本
And consider what’s next, for our kind.
并思考一下 我们的种群接下来会发生什么