我们星球上的生命（2023）

Today,
所有哺乳动物中有五分之一是蝙蝠
one in five of all mammal species is a bat.
但蝙蝠并不是第一个上天的动物
But bats were not the first animals to take to the skies.
经过了整夜的觅食
Having spent the night foraging,
这些果蝠竞相返回巢穴
these fruit bats are in a race to return to the roost...
因为危险会与白天一同来临
...for with daylight comes danger.
鸟类
Birds.
进化出飞行技能远早于哺乳动物
They evolved flight long before the mammals.
比蝙蝠更快更强壮
Faster and stronger than bats...
鹰装备有致命的爪子
eagles are armed with deadly talons.
但随着黄昏降临
But as dusk falls,
天空再次归蝙蝠所有
the skies belong to the bats once more.
数以百万计的蝙蝠展翅高飞
Millions take to the wing,
它们知道 庞大的数量和即将到来的黑暗
knowing that safety lies in numbers
能够带来安全
and in the coming darkness.
在蝙蝠首次上天的同时
At the same time as bats were first moving into the air,
另一些哺乳动物则正在下海
other mammals were moving into the sea...
（4700万年前）
它们被海浪之下的丰富食物所吸引
...attracted by the abundance of food hidden beneath the waves.
哺乳动物进入海洋的过程是渐进式的
The mammals' journey into the oceans was a gradual one.
这是慈母鲸
These are Maiacetus,
身长2.5米 是鲸的祖先
two-and-a-half-meter-long ancestors of the whales.
但与鲸不同 它们多数时间仍懒洋洋地躺在陆地上
But unlike whales, they still spend much of their time lazing on land.
在水中 它们才会活跃起来
It's in the water that they come alive...
追逐鱼群
chasing schools of fish.
它在水下的时间 受限于它能屏住呼吸的时间
His time down here is limited by how long he can hold his breath.
它似乎夹在两个世界之间
He seems caught between two worlds,
尤其是面临危险的时候
especially when facing danger.
哺乳动物的智慧是它唯一的防御手段
The mammal's intelligence is his only defense...
但它不可能永远躲在下面
but he can't stay down here forever.
耳齿鲨
Otodus.
身长是大白鲨的两倍
Twice the length of a great white shark.
凭借敏锐的感官 它能准确地锁定对方的位置
With finely-tuned senses, it can pinpoint his exact location,
而且它并不急于行动
and it's in no hurry to make its move.
慈母鲸的氧气快用完了
The Maiacetus is running out of air.
在开阔水域 无处可逃
In open water, there's no escape.
一个凹岩成为避难所
An overhang offers refuge.
但是快没时间了
But time is running out.
一条海沟提供了掩护
A gully provides cover.
安全了
Safe
又能呼吸了
and able to breathe once more.
哺乳动物想要成为海洋的主宰 还有很长的路要走
Mammals had a long way to go to become masters of the world's oceans,
但这只是时间问题
but it was only a matter of time.
随着地球持续降温
As the planet continued to cool,
生命爆♥炸♥式发展
it fed an explosion of life...
使如今的巨兽得以进化
allowing the giants of today to evolve.
哺乳动物从微小的陆地动物
The mammals had gone from tiny land animals...
变得比恐龙还大
to being bigger than dinosaurs.
通过大口呼吸
With each giant breath,
它们利用氧气的效率远高于慈母鲸
they use oxygen far more effectively than Maiacetus.
而且由于是温血动物
And being warm-blooded,
肌肉始终保持在最佳性能的温度
their muscles are always at a temperature for maximum performance...
所以能够产生持续的能量爆发
...allowing the whales to generate sustained bursts of energy.
在争夺配偶的时候
When competing for a mate,
众多雄性座头鲸会充分利用这项能力
humpback males exploit this ability to the full...
追逐同一头雌鲸
pursuing a single female.
这不仅仅是速度的问题
This is much more than about speed.
雄鲸尽可能靠近雌鲸
The males stay as close to the female as possible
以便雌鲸能够评估自己的力量和耐力
so she can judge their strength and stamina.
喷出气泡
Bubble streaming
恐吓对手
intimidates rivals.
雄鲸互相冲撞
The males plow into each other.
有的落在后面
Some get left behind,
仍在战斗
still fighting.
大部队继续追赶
The main group keeps up the chase...
对雌鲸穷追不舍
hot on the tail of the female.
突然之间
Then suddenly,
雌鲸停了下来
she stops.
停在水中
Hanging in the water...
叫停比赛
she has called off the race.
决定已经作出
She has made her decision...
允许一头雄鲸靠近
and allows one male... to approach.
哺乳动物征服了地球上每一片栖息地
The mammals have conquered every habitat on Earth.
陆地 天空 海洋
Land, air, and sea.
小行星撞击 使哺乳动物从卑微的弱者…
The asteroid strike had allowed the mammals to go from lowly underdogs...
变成了世界霸主
to become a global power.
这就是机遇在地球生命历史中 所扮演的角色
Such is the role of chance in the history of life on our planet.
但是哺乳动物的故事 还有一章仍待讲述
But there is one more chapter in the mammal story still to be told.
250万年前
Two and a half million years ago,
哺乳动物面临一个新的挑战
the mammals were faced with a new challenge.
过去缓慢的地球降温
What had been a slow cooling of the planet
加速了
intensified.
冰河时代♥开♥始
The start of an ice age.
从冰封的废土中 将出现一股新的力量
From its frozen wastes would come a new force...
一种哺乳动物 拥有史上最强的智力和适应性
a mammal armed with more intelligence and adaptability than any before.
这是世界上出现过的最危险的动物
The most dangerous animal the world had ever seen.