我们星球上的生命（2023）

地球历史90%的时间中
For 90% of our planet's history,
温度都太高 无法形成冰冻
it has been too warm for ice to form.
所以 2500万年前 当冰河时代突然袭来之时
So when the Ice Age hit two and a half million years ago,
影响巨大
its impact was huge.
本集讲述的是大冰冻的故事
This is the story of a great freeze
以及一个王朝的兴起
and the rise of a dynasty
将生命推向灭绝边缘
that would bring life to the brink of extinction.
《我们星球上的生命》
双语合并：村儿南
第 8 章：冰与火的世纪
（当今）
黄石国家公园 是美国最寒冷的地方之一
Yellowstone is one of the coldest places in America.
在冬季
In winter,
这里仍经受着 冰河时代带来的冰冻状态
it still endures some of the same freezing conditions that an ice age brings.
温度会降至零下50度以下
Temperatures can drop below minus 50 degrees.
只有为寒冷而生的生物才能存活
Only those built for the cold can survive.
野牛厚厚的皮毛是出色的隔热材料
A bison's thick coat is such good insulation,
所以它们不需要多少能量 就能保持温暖
they need little energy to keep warm...
这也非常重要
which is just as well,
因为冰雪之下很难找到草
as grass is hard to find beneath the snow.
但野牛并不是这里唯一饥饿的动物
But bison aren't the only hungry ones here.
狼也能忍♥受最寒冷的冬季
Wolves can also withstand the coldest of winters...
其在美洲捕杀野牛的历史 已经超过10万年
and have been hunting bison in America for more than 100,000 years.
为了分散野牛群
To split up the herd...
狼群得让野牛群动起来
...the pack needs to get them moving.
恐慌使狼群获得控制权
Panic gives the wolves control.
野牛群必须聚在一起
The herd must stick together.
一次跌倒就可能产生致命后果
One trip could prove fatal.
但野牛不可能永远奔跑
But the bison can't run forever,
尤其是在深深的雪地上
especially in the deep snow.
它们唯一的希望是转身直面对方
Their only hope is to turn and face their pursuers.
这时狼群才会停下脚步
Only then does the pack finally relent.
但无论野牛群去哪里
But no matter where they go,
狼群都会跟随
the wolves will follow.
数千年来 这对宿敌一直缠斗不休
Age-old enemies that have been locked in battle for millennia.
然而它们是幸运的
Yet these ancient adversaries are lucky...
因为可以期待冬天的结束
for they can look forward to the end of winter
和春天的到来
and the relief of spring.
但曾经有一个时期
But there was a time
冬天似乎永远不会结束
when winter never seemed to end.
（250万年前）
250万年前
Two and a half million years ago,
地球轨道、洋流 和二氧化碳水平的变化
changes in the Earth's orbit, ocean currents, and carbon dioxide levels
导致地球温度骤降
led to an abrupt cooling of the planet.
冰河时期开始
The great Ice Age had begun...
从最细微之处开始变化
...and it started with the tiniest of things.
雪花本身就是一个脆弱的冰冻奇迹
On its own, a snowflake is a fragile, frozen wonder.
没有两片雪花完全相同
No two the same.
但是雪花聚在一起 改变了世界
But together, snowflakes changed the world.
没有了温暖的夏季将其融化
Without warm summers to melt them,
白雪覆盖了地球北部
snow blanketed the north of the globe...
经过数千年
...and, over thousands of years,
压缩成了几千米厚的永久性冰层
compacted to form permanent ice sheets several kilometers thick.
在这个寂静的国度
Here, in this silent realm,
冰冻导致生命无法存在
life was frozen out of existence.
但是在冰层以南
But south of the ice sheets,
一个新世界诞生了
a new world was created
生命在这里兴旺发展
where life could thrive.
围绕几乎整个北半球
Circling almost the entire Northern Hemisphere,
冻原成为地球上最广阔的栖息地
the tundra-steppe became Earth's most extensive habitat.
（两万年前）
适应了寒冷的哺乳动物 主宰着这冰雪天地
Mammals that adapted well to the cold dominated these frigid lands...
包括其中最大、最具代表性的…
including the largest and most iconic of them all...
真猛犸象
...woolly mammoths.
它们与大象相似的祖先
Their elephant-like ancestors
在数百万年前离开非洲
left Africa millions of years earlier
进化成了这些高度专门化的巨兽
and evolved into these highly specialized beasts.
长毛 小耳 短尾
Long hair, smaller ears, and shorter tails
有助于在寒冷的环境中保温
help them conserve heat in the cold.
它们由一头年长的雌性即女族长带领
They are guided by an old female, the matriarch,
由其将知识代代相传
who passes her knowledge down the generations.
以确保后代的安全
Generations she needs to keep safe.
穴狮比今天是狮子更大
Bigger than lions today,
能够捕食这种最大的猎物
cave lions can bring down the very largest of prey.
但小一点比较好
But smaller is easier.
无处可躲 大胆的狮子都懒得藏了
With little cover, the brazen cats don't even try to hide.
相反 它们耐心等待时机
Instead, they bide their time, waiting for the right moment.
小象不能掉队
The calf must stay close to its protectors...
但猎手们已经盯上它
but the hunters have him in their sights.
猛犸象排出象牙墙
The mammoths form a wall of tusks...
但狮子却不打算离开
...but the lions aren't going anywhere.
女族长受够了
The matriarch has had enough...
但其中一位猎手发现了一个机会
...but one of the hunters spots an opportunity.
这只小象再也不会离队
The teenager will never stray from the herd again.
现在轮到狮子防守了
Now it's the lions' turn to defend.
小象的母亲
The calf's mother...
知道木已成舟
...knows it's a lost cause.
它们别无选择 只得退下
They have no choice but to back down
继续保护余下的后代
and protect the generations that remain.
它们只能继续迁徙
All they can do is continue their migration
穿过这寒冷的冻原
across the cold tundra-steppe.
尽管冰雪从未覆盖整个地球
While ice never completely engulfed the planet,
但它仍对全球产生了影响
its impact was still felt across the globe...
有时影响极为出乎意料
sometimes in the most unexpected ways.
世界上大部分水被冰封
With most of the world's water locked up as ice,
陆地变得越发干燥
the land became increasingly dry.
这是冰河时代的另一面
This is the flip side of an ice age.
冻原以南
South of the tundra-steppe,
沙漠面♥积♥几乎翻倍
the deserts almost doubled in size,
沿途将一切吞噬
devouring everything in their path.
进化出能承受极端高温的沙漠专家
Only desert specialists that had evolved to withstand extreme heat
才能在如此恶劣的条件下生存
could survive such hostile conditions.
但干旱并未止步于此
But the drying didn't stop there.
进一步向南 非洲的热带雨林
Even further south, Africa's tropical rainforests,
为生命提供稳定的庇护所 超过5000万年
stable sanctuaries for life for over 50 million years,
如今几乎完全消失
almost completely disappeared...
被一大♥片♥干燥的森林和草原所取代
...replaced by a vast expanse of dry forest and grassland.
这对生命影响巨大
The impact on life was huge,
尤其是对这一类动物
not least on one group of animals...
灵长类
...the primates.
狒狒有94%的DNA与我们相同
Baboons share 94% of their DNA with us,
也与我们有一段共同的经历
as well as a crucial part of our story.
从树上下到森林地面生活
The descent from the treetops to a life on the forest floor.
在冰河时期 我们的表亲在这里面临许多新的挑战
Down here, during the Ice Age, our cousins faced many new challenges.
地上的生活更危险
Life on the ground is more dangerous...
这里是大型捕食者的家园
...home to large predators.
幸运的是
Fortunately,
灵长类虽然在力量和体型上有所不足
what primates lack in strength and size,
但我们能用 智慧和庞大的家族进行弥补
we make up for with intelligence and large families.
但是为众多家族成员找到足够的食物
But finding enough food to feed many mouths...
是一项持续的挑战
...is a constant challenge.
所以找到食物时
So when food is found,
就会引起各方注意
it attracts plenty of attention.
哪里有宝贵的资源
And where there's a precious resource...
冲突就不可避免
...conflict is inevitable...
尤其是同类之间
...not least with your own kind.
一群敌对狒狒
A rival troop
对分享毫无兴趣
with no appetite for sharing.
在旱生林
In the dry forest,
每一颗果实都值得为之战斗
every fruit is worth fighting for...
每一次战斗都非常重要
...and every fight counts.
敌对狒狒群及时止损
The rival troop cut their losses.
但它们会回来
But they'll be back.