生命的进化（1979）

we can remain active and we can live in cold climates.
但是为了这些特权我们付出了很高的代价
But the price we pay for those privileges is very high.
譬如我们吃的食物的80%的能量
Something like 80% of the energy in the food we eat
都被用来维持我们的体温 使其保持在38摄氏度左右
goes to maintaining our body temperatures at around 38 degrees centigrade.
爬行动物的系统是直接从太阳获得能量
The reptiles' system, getting heat directly from the sun,
这更经济
is much more economical.
一只爬行动物生存下来 只需要同样大小的哺乳动物食物需求量的10%
A reptile can survive on 10% of the food a mammal of a similar size would require.
因此，尽管它们不能生活在北极
And so, although they can't live in the Arctic,
它们能依靠低热量的食物生活 像海鬣蜥以海草为生一样
they can survive on low-calorie foods, like the seaweed these marine iguanas eat,
而且能生活在很多食物稀少的地方 像沙漠
and live in great numbers in places where food is very scarce, such as deserts.
例如一只变色龙在荒地里还能活跃
A chameleon, for example, can flourish in barren areas,
每几天提供给它的是 它抓到的一只适当大小的虫子
provided that every few days it catches one reasonably-sized insect.
变色龙变色的才能
The chameleon's talent for changing colour
不仅给了它不同的伪装还表达了它的情感
serves not only to give it different disguises but to express its emotions.
愤怒时它会变黑，求爱时则是鲜亮的色彩
It goes black with rage and becomes brightly coloured when courting,
像很多爬行动物一样
as many reptiles do.
奥努里斯蜥蜴展示它可扩张的袋状喉咙
Anolis lizards display with extensible throat pouches,
每一种都有着自己特殊的颜色
each species with its own particular colour.
点头加强了效果它就像挥舞旗帜
Nodding reinforces the effect. It's like waving a flag.
这是来自斐济的稀少的绿鬣蜥
This is the rare green iguana from Fiji.
它示爱的色彩将持久展示 因为只有雄性才有黑色条纹
His courting colours are permanently on display, for only the male has black stripes.
它没有袋状的喉咙，但是像很多蜥蜴一样
He doesn't have a throat pouch, but, like many lizards,
当一个雄性处于繁殖状态时 它用点头表示自己的情况
uses head nodding to signal his status as a male in breeding fettle.
相比较而言，雌性比较挑剔， 而且几乎不是很易动感情
By comparison, the female is plainer and not nearly so demonstrative.
加拉帕戈斯群岛鬣蜥也点头
The Galapagos iguanas also nod.
对于它们来说，这姿势有着双重作用
For them, as for others, the gesture serves a double purpose:
不仅给雌性以很深的印象 还警告了竞争的雄性
not only to impress the females, but to warn off rival males.
每一种都有自己的节奏
Each species has its own rhythm.
陆地鬣蜥有一种稍微不同的语言
The land iguanas have a slightly different language.
鼻对鼻的碰撞过程 足够解决雄性间的领地纠纷
A nose-to-nose nodding session is enough to settle a territorial dispute between these males.
显然，所有这些表现都使问题获得了圆♥满♥的解决
Eventually, all these displays lead to the desired consummation.
爬行动物是第一批脊椎动物 为此体内受精就是必须的
The reptiles were the first vertebrates for whom internal fertilisation was essential.
它们直系的祖先，两栖类，就没这种需求
Their immediate ancestors, the amphibians, had no need for it.
它们在水中交♥配♥， 而从体内排出的精♥子♥就会游向卵
They mated in water, and sperms shed from the body could swim to the eggs.
但是在干燥的陆地上 雄性爬行动物就不得不去找
But out on dry land, the male reptiles had to find
一些其他的方法让精♥子♥遇到卵
some other way of ensuring that sperm met egg:
通过把它排放到雌性的身体内
by placing it inside the female's body.
有时看起来，对这些古老动物的那个过程
And it sometimes seems that that process for these antique creatures
仍然是个很笨拙，费力的事情
is still a very clumsy and laborious business.
在预期的过程中， 那导致了爬行动物的第二次伟大变革
In due course, that produces the second of the great reptilian innovations.
它们不透水的皮肤 使它们能生活在地球上最干燥的地方
Their waterproof skins had enabled them to live in the driest places on earth.
但是那种价值是有限的 如果它们不得不退却
But that was of limited value if they had to retreat
去寻找开阔的水域产卵 如同两栖动物不得不如此
to find open water in which to lay eggs, as the amphibians have to do.
爬行动物通过生产这个解决了那个问题
The reptiles solved that problem by producing this.
不透水的蛋
The waterproof egg.
实际上，它像一个 由羊皮纸和贝壳压缩而成的小水池
In effect, it's a tiny pond encapsulated in parchment and shell
它们的幼崽能在其中穿梭 也就相当于是蝌蚪阶段
in which their young can pass through what amounts to the tadpole stage.
斐济绿鬣蜥只产两个或三个蛋
The Fijian green iguana lays only two or three eggs,
同时细心地将它们埋进土壤里
burying them with care in the ground.
所有的爬行动物的蛋一经孵出就构造完全了
From all reptile eggs, the young clamber out, fully formed,
实际上完全是它们父母的缩小版 而且准备着接下来的行动
virtually exact miniatures of their parents and ready for immediate action.
这些就是小蜥蜴
These are baby skinks.
从像这样的一个蛋中 曾经孵出了所有最为壮观的爬行动物中的一员
From an egg like this there once hatched one of the most spectacular reptiles of all.
因为这是一个已成化石的恐龙蛋
For this is the fossilised egg of a dinosaur.
这些早期爬行动物的成功将没有问题
There can be no question of the success of these early reptiles.
它们统治这个世界1亿3千万年
They dominated the world for 130 million years.
在那段时间里，它们形成了各种样子和大小
During that time, they developed into all kinds of shapes and sizes.
很多消失了，一些尚存的成为最大的飞禽
Many took to the air, and some were the biggest flying animals to have existed,
有着像飞机一样的大翅膀
with a wingspan as big as a small aeroplane.
其他的一些转向海洋
Others even returned to the sea.
一些用巨大的鳍状肢划着水
Some rowed themselves along with huge flippers,
而一些则像今天的海豚一样用尾巴划水
while others sculled with their tails as dolphins do today.
而乌龟则长成小船的大小
And turtles grew to the size of a small boat.
从蛋孵出恐龙的年代
From eggs hatched the dinosaur dynasty,
那是爬行动物成功的最为壮观的典范
which was the most spectacular demonstration of reptilian success.
侏罗纪时代
Deinonychus.
暴龙家族
Tyrannosaurus rex.
长有三只角的恐龙，即三角龙
The three-horned dinosaur, triceratops.
剑龙，龙栉龙，
Stegosaurus, parasaurolophus.
以及腕龙，身体如同♥房♥♥屋一样大
And brachiosaurus, as big as a house.
这些是曾经踏步于地球 给人最深刻印象的动物中的一些
These were among the most impressive animals ever to tread the earth.
而我们是从它们的骨头来了解它们的
And we know them from their bones.
这是迄今为止发现的最为丰富的恐龙骨沉积
This is the richest deposit of dinosaur bones yet discovered.
它在美国西部的犹他州
It's in Utah, in the western United States,
1亿4千万年前，当恐龙处于繁盛时期
and 140 million years ago, when the dinosaurs were at their prime,
我们描叙的面前的雄伟的悬崖 还处于地平线以下
this great cliff face, which is now tilted, lay horizontally.
这石头还是一条宽阔的河流中心的 沙洲上的松松的沙子和砂砾
This stone was the loose sand and gravel of a sandbank in the middle of a wide river.
在那条河的下边漂浮着 那个巨大的，肿胀的，腐烂了的尸体
Down that river floated the great, bloated, rotting carcasses
巨大的恐龙的尸体
of huge dinosaurs.
它们中很多在河岸边搁浅了 现在这儿就是它们骨头所呆的地方
And many of them got stranded on this river bank, and here their bones lie.
它们所在的地层只有12英尺厚
The layer in which they lie is only about 12 feet thick.
据推测它们大约100年才沉入这个空间
It's thought it was all laid down in the space of 100 years or so,
在这期间它们的状况给人丰富的联想
which gives some idea of how abundant they must have been at the time.
长骨：腿骨和双臂
The long bones: the leg bones and the shoulder blades
还有尾巴和尾骨，都大略指向这个方向
and tails and backbones, are all roughly pointing in this direction.
那使河流的流向变得很明晰
That makes it pretty clear that the river current flowed this way.
这是一个剑龙的骨盘 在它的背部有两排对称的叶片
This is a plate from a young stegosaurus, the one with two rows of blades on its back.
这是一头凶猛的异龙的牙齿
And this the tooth of a savage allosaurus.
在这个区域里已经发现了14种不同的恐龙
14 different species of dinosaur have been found in this quarry,
范围从不大于一只鸡的小恐龙
ranging from tiny creatures no bigger than a chicken
到有着如此巨大腿骨的真正的怪兽
to real monsters like the animal to whom this enormous thigh bone belonged,
它是迄今为止见到的最大的陆地动物之一
which was one of the biggest land-living animals the world has seen.
在这个石坑里大部分骨头保留了下来
Most of the bones left in this quarry
来自被河流或者食腐爬行动物肢解的尸体
come from carcasses dismembered by the river or by scavenging reptiles,
但是直到19世纪20年代这里的挖掘工作才结束
but by the time quarrying finished here in the 1920s,
大约有30个基本完整的骨架被拿走
over 30 near-complete skeletons had been taken away,
而且它们中的很多最美丽的 最吸引人的恐龙骨架在我们今天的博物馆里
and many of the most beautiful and impressive dinosaur skeletons in our museums today
来自这个石坑或者其他的传递着同样的信息
come from this quarry or from others working in the same formation.
雷龙，它们中最大的一种
A brontosaurus, one of the biggest of all.
长超过60英尺，体重达30吨♥
Over 60 feet long and weighing in life about 30 tons,
而三头强壮的公象才能达到约这个标准
about the same as three full-grown bull elephants.
问题立即浮现：为什么这些植食恐龙
The question immediately arises: why did these vegetable-eating dinosaurs
能长成如此巨大的体型？
grow to such a gigantic size?
最少存在两种可能的答案
There are at least two possible answers.
一种与它的食物相关， 即它吃的是苏铁类和蕨类植物
The first concerns their food, which was cycads and ferns.
这种食物很粗糙，含有纤维质， 消化很费力
Those sort of plants are tough and fibrous and take a great deal of digestion.
这种恐龙只有些不太适宜咀嚼的 很弱小的牙齿
The dinosaurs only had relatively feeble teeth which weren't much good at mastication,
所以它们就需要很大的胃作为发酵桶
so they had to have huge stomachs which would serve as fermentation vats
在那里食物被保留很长时间直到消化掉
in which the food could be kept for long periods of time while it was digested.
一个巨大的胃需要由巨大的身体持带
A huge stomach requires a huge body to carry it.
第二种原因是所有爬行动物都得不断面对的：
The second reason concerns that recurring problem for all reptiles:
温度控制
temperature control.
你的身体越大，你受气候的影响就越小
The bigger your body, the less susceptible it is to variations in temperature
因为它能更久地保持体温
because it retains its heat longer.
温度控制可能是另一种著名的恐龙奇异身体的解释
Temperature control may be the reason for the bizarre body of another famous dinosaur,
即剑龙
the stegosaurus.
过去常说这些盘状物是一种盔甲
It used to be said that these plates were a kind of armour.
但是近期研究发现那里曾经 覆盖着充满血液的厚厚的皮肤
But close examination has shown that they were covered with a skin thick with blood.
所以如果这种动物侧面朝向太阳 它将成为太阳能板了
So if the animal were broadside onto the sun, they would serve as solar panels,
快速地加热血液
rapidly warming the blood.
而且如果它过热且还沐浴在阳光中 它们又变成散热器
And if it were overheated and faced into the sun, they would serve as cooling radiators.
这种改变温度的能力是难以估价的
Such an ability to influence temperature could have been invaluable.
当然，在凉爽的清晨，对于一个植食者来说 行动的迟缓可能将是灾难
Certainly, for a plant eater to be sluggish on a cool morning could've been disastrous.
在德克萨斯州的下面， 一个河口的泥沙现在已经变成岩石，形成河床
Down in Texas, the muds of an estuary, now turned to rock and forming a river bed,
保留了这些动物最为鲜明的记录
preserve a vivid record of these creatures.
这是一个肉食恐龙的脚印 一个捕食者
This is the footprint of a flesh-eating dinosaur, a hunter,
在它的两脚上有巨大的爪子
with huge talons on its two feet.
它直立起来，大约有10到12英尺高
It stood on its two feet, upright, about 10 or 12 feet tall,
它的尾巴拖在地上，现在已深深的嵌入了泥沙
with its tail on the ground, which here has ploughed into the mud,
产生了巨大的沟
throwing up this great furrow.
这里有它们中的两个以上