生命的进化（1979）

火山在现今的活动很微弱
The volcanoes of today are mere feeble flickerings
与它刚开始时支配地球的历史相比
compared with those that dominated the world at the beginning of its history.
在那时，从火山口涌出巨大的熔岩
Then, enormous sheets of lava welled out of craters,
剧烈的爆发使山变为碎片
titanic explosions blew mountains into fragments
散开的碎片化做尘土和灰烬覆盖地面
and scattered them as dust and ash over the surface of the land.
那样的活动持续了上亿年
That sort of activity continued for millions and millions of years.
我们来谈谈关于45亿年前的那个时代
I'm talking about a period that was 4,500 million years ago.
侵蚀的力量，霜和雨、雪和冰
The forces of erosion, frost and rain, snow and ice,
使火山岩化为碎片
shattered the volcanic rocks into fragments.
河流把碎片带到了大♥陆♥的边缘
Rivers carried them down to the edges of the continents
将它们沉淀下来成为沙子、沙砾、泥土
and deposited them as sands and gravels and muds.
当陆地板块沿着地球漂移并且碰撞时
As the continents drifted over the globe and collided,
形成新的山脉，并且轮依次被侵蚀
new mountain ranges were built up and, in their turn, worn down.
经过这一漫长的时期陆地依然贫瘠
And throughout this immensity of time, the land remained sterile.
什么都没有， 甚至是最小的动物和极小的绿色斑点
Nowhere was there even the smallest of animals or the tiniest speck of green.
如果你浓缩整个生命的历史
If you condense the whole history of life,
从它开始到现在，浓缩成一年
from its beginnings until the present moment, into a year,
那么不到九月末
then it wasn't until the end of September
水母等最初的动物出现在海洋
that the first creatures of any size, jellyfish and so on, appeared in the sea.
并且直到到十一月初 才在陆地上出现最初的生命
And it wasn't until the beginning of November that the first life,
一些绿色的斑点
a few patches of green, appeared on land.
也许在水的边缘，就像这样
Maybe at the edge of water, like this.
这些最初的植物是一些简单的藻类
These first plants were simple algae
它们已经发展出了足够厚的细胞壁， 使它们能在潮湿的石头和沙砾中存活
that had developed cell walls thick enough for them to survive on moist boulders and gravels.
它们在沙滩和沙嘴上缓慢地蔓延
Slowly, they spread over the lake beaches and sandspits,
伟大的革命先驱者引导出绿色的世界
pioneers of the great revolution that was to lead to the greening of the earth.
最初的森林
移出水面对植物来说出现了很多问题
Moving out of water for the plants presented a number of problems.
其中一个最严重问题就是维持生命
One of the most serious was the question of support.
在水中，海藻这类生物可以长成长长的线状
In water, algae like this can grow into long strands,
但是缺少水的支撑，也没有很硬的茎
but robbed of the support of water, none has a sufficiently rigid stem
让它们垂直生长
to allow it to grow upright.
所以最初的陆地植物仍是很低级的
So the first land plants remained lowly,
形成像地钱一样平坦的外皮 或是像苔藓一样的垫子
forming flat skins like liverworts or cushions like mosses.
它们全都生活在潮湿的地区 由于一个很好的理由
All of them lived in wet, moist places and for a very good reason.
它们的祖先，海藻， 用两种方式进行了繁殖，发芽和有性繁殖
Their ancestors, the algae, had reproduced in two ways, by budding and sexually,
并且，有性繁殖方法使生殖细胞
and the sexual method involved sex cells
在水中游动，彼此寻找并融合
swimming through water to find one another and fuse.
而苔藓，保持了与此很相似的方法
Well, mosses retain very much the same sort of method.
这使它们在水中结合在一起
It's this that keeps them tied to water.
这使它们只能生活在那些， 至少在一年中有一段时间是湿润的地方
So they can only live in places where at the very least it's wet during some time of the year,
使有性繁殖可能发生
so that sexual reproduction can take place.
当然，在那些地方它们逐渐适应周围的环境
Of course, in places like this, they are literally in their element.
苔藓和地钱都像这样产生两种生殖细胞
Mosses and liverworts like this both produce two kinds of sex cells.
只有几公分高的地钱最终 发育出极小的，可移♥动♥的精♥子♥
These outgrowths on the liverwort, only a few centimetres high, develop tiny mobile sperms
它们积极地游动
which actively swim.
这些不同的发育， 包括更大的静止的生殖细胞，卵
These different growths contain larger static sex cells, the eggs.
在显微镜下， 你可以看到这些卵以微小的细管为基础
Under the microscope, you can see the eggs at the base of tiny tubules
被由较小细胞组成的外壳围绕
surrounded by a protective sheath of smaller cells.
当卵子成熟，并且环境足够湿润，授精开始
When the outgrowths are ripe and conditions sufficiently wet, fertilisation begins.
蜿蜓活动的精♥子♥被释放 并在覆盖植物的薄薄的水层上游动
The wriggling sperm are released and swim in the film of water that covers the plant.
精♥子♥表现为一种乳白色的流动
The sperm appears as a milky fluid.
同时，作为雌体部分的地钱负担卵细胞
At the same time, the female part of the liverwort that bears the egg cells
释放一种特别的吸引精♥子♥的化学物质
releases a special chemical that attracts the sperms.
最终，它们到达雌体器官
Eventually, they reach the female organs.
受精发生，卵开始发育
Fertilisation occurs and the eggs develop,
并反复地分♥裂♥制♥造♥一个由显微颗粒组成的壳囊， 这就是孢子
repeatedly dividing to produce a capsule full of microscopic grains: spores.
当它们成熟并且天气干燥，壳囊破裂
When they are ripe and the weather is dry, the capsules burst.
每一份孢子都可能长成一个新的地钱植物
Each minute spore is capable of growing into a new liverwort plant.
苔藓也是通过这两种交互的方法繁殖
Mosses also reproduce by these two alternating methods.
为了演化， 有性繁殖阶段产生了各种各样必要的后代子孙
The sexual stage provides the variety of offspring necessary for continued evolution.
无性生殖的孢子可以随风散布到很远的距离
The asexual spores can be carried on the wind to distribute the plant over great distances.
苔藓的孢子的壳囊在形状上是各式各样的
The spore capsules of mosses are varied in shape,
并且它们有独特的办法 确保它们能释放它们的种子
and they have ingenious ways of making sure they only release their contents
当气候适宜的温暖潮湿的时候
when the weather is suitably warm and dry.
许多种群有可以分离的冠部 并能在孢子被散放前就裂开
Many species have detachable caps which are blown off before the spores are released.
在那下面是一个像胡椒罐子一样穿孔的盖子
And beneath, a perforated lid like a pepper pot.
风就会携带微小的孢子到几米远的距离
The wind will now carry the microscopic spores for miles.
正是由于这种结构最初的植物 向地球上潮湿的地方拓展
With such mechanisms as these, the first plants colonised the moist places of the world
并且绿色植物连接湖和河流
and green carpets bordered the lakes and rivers.
将它们连结成为生成动物的微小森林
Into these miniature jungles came the first land animals.
倍足纲节动物和现在一样，是食草动物
Millipedes, then as now, were vegetarians,
而且它们一定在苔藓和地钱中找到丰富的食物
and they must have found plenty to eat among the mosses and liverworts.
最大的纲节动物在今天也只有几英寸长
The biggest today are only a few inches long,
但是一些生命的先驱者 它们的远古形态长的非常的巨大
but many ancient forms that pioneered life on land grew very much larger.
一只可以像牛一样长
One, indeed, was as long as a cow.
倍足纲节动物是从海洋生物的同一个 祖先演化而来，和甲壳类有着疏远的联♥系♥
Millipedes were descended from sea-living creatures distantly related to crustaceans.
从它们那里， 甲壳类动物遗传到节状的身体和一个外部的骨架
From them, they inherited segmented bodies and an external skeleton
外部的骨架给了它们保护， 使它们在空气中，陆地上也可以移♥动♥
which gave them support so they could move just as well in air, on land,
像它们的祖先在水中移♥动♥一样
as their ancestors had done in the sea.
但是，呼吸是另一个问题
But breathing was another matter.
它们的祖先用在腿边的柔软的腮 从水中萃取氧气
Their ancestors had extracted oxygen from water with feathery gills alongside each leg.
但是同样的事情在空气中却不能做到
But such things wouldn't work in air.
最初的倍足纲节动物 发展出在每一个节里含有分支的管子
Instead, the first millipedes developed a system of branching tubes within each segment,
沿着这些管子，空气在身体中的各个部分散开， 使组织可以直接吸收氧气
along which air diffuses to all parts of the body so the tissues can absorb oxygen directly.
那些管子通过在每个节旁边的 微小的毛孔对外开放
These tubes open to the outside through a tiny pore on the side of each segment.
但是放眼浏览， 没有倍足纲节动物长久生存的环境
But the amiable browsing millipedes didn't have the land to themselves for long.
在它们发展不久，捕食它们的猎手出现了
Very soon after they had colonised it, hunters came up from the sea to prey on them.
那些猎手们在今天，仍然积极地活动， 通常是在晚上
These hunters are still today active, mostly at night.
蝎子
The scorpions.
它们已经从一个 不同的节状海洋动物群体中进化出来
They had evolved from a different group of segmented sea creatures,
再一次， 它们有了一个在陆地上可以有效工作的外壳
but again they had an external skeleton which worked effectively on land.
它们有锋利而有力的爪子尾巴上有有毒的刺
With powerful nipping claws and poisoned stings on their tails,
蝎子是有充分的武器并凶残的
scorpions are well-armed and ferocious,
积极的寻找猎物无论猎物躲藏在哪
actively seeking out their prey wherever it may be hiding.
另一类密切联♥系♥的族群 在微小的森林中进化为白天的猎手
Another closely related group became day hunters in the miniature forests.
蜘蛛
The spiders.
虽然它们海洋生活的祖先有很多条腿
Although their sea-living ancestors had many legs,
蜘蛛和蝎子只有四双 速度上更快了
spiders and scorpions have only four pairs. Better for speed.
在蜘蛛的身体上已经失去了很多分割的标记
Spiders have lost most signs of division in their bodies,
除了一些在东南亚生长的一些古老的种类
except for some primitive ones that live in South-East Asia.
它们的腹部显示了祖先分割的最后的一点痕迹
Their abdomens show the last relics of that ancestral segmentation.
在早期，蜘蛛在腹部生成腺
Early on, the spiders developed glands in the abdomen
它们用腺产生丝
with which they produce silk.
它们用丝猎捕， 有时候它们放出长丝线来走远路
They use it in hunting, sometimes laying long trip lines,
有时候它们制♥造♥密集的薄网
sometimes constructing dense sheets.
它们熟练地用改进的肢喷丝头，来操纵细丝
They manipulate the threads with modified limbs, the spinnerets.
在网完成的时候， 任何微小的生物试图通过这里
By the time it's finished, any small creature trying to make its way here
都会落人一个柔软光滑的陷阱
will blunder into a silken trap.
而当它们仍然被缠着的时候蜘蛛会突袭它们
And while it's still entangled, the spider will pounce on it.
繁殖对所有的陆地生物来说意味着新的问题
Reproduction for all these land creatures presented new problems.
没有水将精♥子♥输送到卵子 它们毫无办法，除了：
Without water to transport sperm to egg, there was nothing for it:
雄性和雌性结合
male and female had to get together.
对倍足纲节动物来说这并不意味着真正的危险
For the millipede, this presented no real danger.
它们是草食性动物， 所以当个体相遇时没有被对方吃掉的危险
They're vegetarians, so when individuals meet, neither risks being eaten by the other.
它们的困难完全是操作问题
Their difficulties are entirely ones of manipulation.
雄性和雌性的生殖腺都在第二双腿的底部
The sex glands of both male and female are at the base of the second pair of legs.
雄性已经用它的第七双腿到达了前方
The male has reached forward with his seventh pair of legs
并且从它的第二个肢节上收集一些精♥子♥
and collected from his second segment a packet of sperm.
现在，如果只有它可以把它们放到正确的位置
Now, if only he can get it into the right position
雌性第二个肢节旁边的卵囊
alongside the female's pouch in her second segment,
一切都很顺利
all will be well.
并且它就是这个样子
And there it goes.
蝎子的繁殖问题更加复杂
The scorpion's sexual problems are much more complicated
并有潜在的危险
and potentially dangerous.
那些猎手必须确定一个 并没注意到另一个
These hunters have to make sure one doesn't regard the other
不是作为配偶而是作为一餐
not as a mate but as a meal.
求爱期是必要的，在许多运动中被仪式化
Courtship is necessary, ritualised in a number of set movements.
首先，那些危险的钳子必须被中立
First, those dangerous pincers have to be neutralised.
现在，钳子被禁止行动 更多仪式紧随其后
Now, with the pincers held out of action, more rituals follow.
雄性和雌性的头互相接近