史前星球（2022）

you should never stray too far from Mother.
由于岛上的食物有限
With limited food on the island,
体型小对侏儒猛犸象来说是一种优势
being small works well for dwarf Stegodon.
但在南美大♥陆♥
But here in South America,
冰河时代造就了巨型生物
the Ice Age has made giants.
剑齿虎是一种拥有如剑般利齿的猫科动物
Smilodon, a saber-toothed cat.
它的祖先从北美迁徙而来
His ancestors traveled here from North America,
如今 它是这片新大♥陆♥的王者
and in this new land, he's the king.
当地的竞争者登场
The local competition.
恐鸟
A terror bird.
它也许并没那么可怕
Maybe not that terrifying,
但却是一只聪明 足智多谋 且不会飞的猎手
but intelligent, resourceful, flightless hunters.
它们的祖先在这里生活了五千万年
Their ancestors have lived here for 50 million years.
这是它的兄弟
His brother.
它们会一起狩猎
They hunt together,
但在食物短缺时 恐鸟都会以自己为先
but when food is scarce, it's every terror bird for himself.
但也许剑齿虎能帮上忙
But maybe the sabertooth can help.
既然剑齿虎愿意干这辛苦活 恐鸟又何必亲自动手
Why do the hard work when someone else can do it for you?
它只需要尾随就行了
All he has to do is follow.
别跟得太近
Not too close.
它的兄弟也打着同样的算盘
His brother has the same idea.
剑齿虎前肢粗壮有力
Smilodon have huge, muscular forelimbs
爪子比任何现代猫科动物都大
and paws bigger than any living cat.
正适合用来捕杀这类体型的猎物
Perfect for bringing down prey this size.
如果它够聪明
If he's smart…
就会让它的兄弟当靶子
he'll let his brother take the heat.
场面一片混乱
Chaos!
但计谋得逞
But it's working…
它俩双双受益
for both of them.
王者被两只鸟耍得团团转
The king has been outsmarted by a couple of birds.
但随着冰河时代的动荡持续
But as the turmoil of the Ice Age continues,
各地的动物都必须奋力抗争
animals everywhere will have to fight
才能在这陌生的新世界中保住一席之地
to keep their place in this strange new world.
（下集预告）
就在遥远的北方被冰雪覆盖之际
As the far north freezes,
南方却遭干旱肆虐 沙漠之地不断扩张
in the south, drought rules and deserts expand.
极端的生活环境造就了
The extreme conditions forge
这世界上最奇特的一批生物
some of the strangest creatures the world has ever seen.
为了生存
To survive,
它们必须在数百万年来 最干旱的气候中奋战
they must battle the driest climate for millions of years.
当人们开始研究冰河时期的动物时
When people began studying Ice Age animals,
他们发现了一件奇怪的事
they noticed something strange
那就是 这些动物的化石 在世界各地分布得很奇怪
about the way their fossils were scattered across the world.
其中一个真正令人惊讶的发现是…
One of the real surprising discoveries was
有些本应只存在于特定大♥陆♥的动物化石
that animal fossils associated with certain continents
却在其他地方被发现
were found in other places.
显然 这些动物曾经迁徙…
Clearly, the animals had moved
（古生物学家 达伦奈什博士）
从一个大♥陆♥迁移到另一个大♥陆♥
from one continent to another.
看来这些动物似乎曾横渡浩瀚的海洋
It seemed as if animals were crossing vast oceans.
它们是怎么做到的
How did they get there?
（冰河时代的巨兽是如何跨越地球的 ）
很难想象动物能跨越海洋
It's hard to imagine that animals could cross oceans
前往新的大♥陆♥定居
to settle in new continents,
但在冰河时代期间 出现了一种令人惊讶的现象
but something surprising was happening during the Ice Age
或许可以解释这一切
which could explain it.
在冰河时代较寒冷的时期
During colder periods of the Ice Age,
水结成了冰 并被封存在两极的冰盖中
water becomes ice and gets bound up in ice sheets at the poles.
随着这些冰盖缓慢却持续堆积
Slowly but surely as those ice caps build up,
海洋中的水量也减少了
it means there's less water in the ocean
（气候科学家 艾拉吉尔伯特博士）
这意味着海平面开始下降
and that means that the sea level starts dropping.
而随着海平面的下降
And as you lower sea level,
海床被暴露在外
the seabed is exposed.
海床变成了陆地
Seabed becomes land.
这就意味着 原本分离的陆块
And that means that previously disconnected land masses
突然之间被连接了起来
suddenly are joined together.
在整个地球上
Across the planet,
各个大♥陆♥以不同的方式连接在一起
continents were joining together in different ways.
今天的北美洲和亚洲 是两块不相连接的大♥陆♥
North America and Asia today are physically separate continents,
（地球科学家 克里斯杰克逊教授）
但在冰河时期 海平面下降了100多米
but back in the Ice Age, sea level was a hundred plus meters lower,
而这两个陆块实际上 通过一座陆地桥连接在了一起
and those two land masses actually became connected via a land bridge.
随着这些陆地桥露出海面
As these land bridges emerged out of the sea,
就像是打开了一扇大门
it was like opening a door.
所有动物都可以突然从一个大♥陆♥
All these animals could suddenly move from one continent
迁移到一个全新的大♥陆♥
into an entirely new continent.
但事情并不那么简单
But there was a complication.
这些陆地桥并不是永久存在的
The land bridges were not permanent.
随着冰层开始融化
As the ice kind of started to melt away,
它们会再次沉入海底
they'd disappear under the waves again.
因此动物们
And animals, therefore,
在地球历史上几乎只有一个短暂的时期
had almost a brief window in Earth history,
让它们可以在这些大♥陆♥之间移♥动♥
in which to move between those land masses…
然后再次发现自己被隔离
before finding themselves isolated once again.
在地球的其他地方 一种截然不同的陆地桥
Elsewhere, a different kind of land bridge was forming
正以更加爆♥炸♥性的方式形成
in a much more explosive way.
地球其实是个高度动态的星球
The planet is very dynamic.
当今的它看起来很稳定 但实际上 所有的大♥陆♥板块都在移♥动♥
It feels stable today, but actually, all the continental plates are moving.
当大♥陆♥移♥动♥时 就会产生大量火山
When the continents move, we generate lots of volcanoes.
这一点对于南北美洲来说尤其重要
And this is really important to the North and South American continents,
数百万年前 它们还是两块分离的大♥陆♥
which were physically separate millions of years ago.
移♥动♥的构造板块导致火山爆发
Moving tectonic plates caused volcanoes to erupt,
形成了一条新的陆地带 连接了大♥陆♥之间的空隙
bridging the gap with a new strip of land,
这就是今天的中美洲
which is now Central America.
这陆地带实际上 成为了动物的一条高速公路
It effectively formed an animal superhighway.
不同类型的陆地桥 使动物得以跨越大♥陆♥迁徙
Different kinds of land bridge enabled animals to move continent,
而这所带来的影响非同凡响
and the impact was extraordinary.
生活在北半球的动物得以向南迁徙
Animals living in the Northern Hemisphere were able then to move southwards,
寻找它们迫切需要的生存资源
finding resources they desperately needed,
却也与南美洲的原生动物发生冲突
but coming into conflict with all of the animals in South America.
新的捕食者出现了 它们找到了新的猎物
New kinds of predator arrived and found new prey to hunt.
像后弓兽这样的生物很容易成为捕猎目标
Creatures like Macrauchenia became easy victims.
当这些动物群体迁移到全新的区域时
As you had these animal groups moving into entirely new areas,
它们之间就会出现全新的互动方式
then you would've had entirely new kinds of interactions.
捕猎群拥有如此丰盛的食物
Hunters had such an abundance of food
它们逐渐进化成了 各自物种中体型最大的那个
they gradually grew into the largest of their kind.
一些动物从北美向南迁徙
While some animals came down from North America,
而另一些则从南方向北前进
others were heading up from the south.
这是一场双向流动的迁徙
Traffic flowed in both directions
被称为南北美洲生物大迁徙
in a movement known as the Great American Interchange.
如今 我们一些最具代表性的动物
Today, some of our most iconic animals are descendants
就是那些曾迁徙到新大♥陆♥的物种的后代
of species that made journeys to new lands.
美洲狮 美洲豹
Pumas, jaguars,
还有豪猪 犰狳等哺乳动物
and other mammals like porcupines and armadillos
都是这次伟大迁徙的成果
all result from this great migration.
动物们以新的方式在地球各地定居
Animals settled across the planet in new ways
这一切都归功于冰河时代
all thanks to the Ice Age.