生命的进化（1979）

which does not rear its young in a pouch, is remarkably close.
尽管有不同的祖先， 它们的进化过程为了适应相似的生活方式
The processes of evolution, even when working on different stocks,
仍然趋向于创造了相似的动物
tend to produce similar creatures to fit similar ways of life.
袋狼和狼都是行动迅捷的肉食性动物
The thylacine and the wolf are both swift-running flesh-eaters,
它们看起来也非常相似
and, consequently, they look very much the same.
在哺乳动物和有袋动物之间 还有几种其他的相似品种
There are several other such parallels between marsupials and other mammals.
袋食蚁兽有长长的鼻子和长长的粘舌头， 像穿山甲
The numbat has an elongated nose and a long sticky tongue, like a pangolin,
以白蚁和蚂蚁为生
so it's no surprise to find that, like a pangolin, it feeds on ants and termites.
最相似的一种动物
One of the closest parallels of all
出现在澳洲夜晚的桉树上
appears in the eucalyptus trees of Australian forests at night.
这种小有袋动物被称为“食糖滑翔机”
This little marsupial is called a sugar glider, and with good reason.
不论是外貌还是特殊的技巧
In both its appearance and its acrobatic skill
都和北美的飞松鼠难以分辨
it's almost indistinguishable from the flying squirrel of North America.
它们的脚趾间都有宽大的皮翼
Both have a wide flap of skin between their legs
依靠空气能够滑翔很长的距离
that catches the air and enables them to glide great distances.
在澳洲的进化并没不是一直创造和其他地方
Evolution in Australia has not always produced such close parallels
如此相似的动物
to its products elsewhere.
比如，树袋熊
This, for example, is the koala.
生活在树上，除了几种特定的树叶什么也不吃
It lives in trees and eats nothing but the leaves of just a few particular kinds.
南美的树懒和他差不多
Sloths in South America do much the same
对树叶也很挑剔，非洲的一些猴子也这样
and are equally fussy about their leaves, and so are some monkeys in Africa,
但他们和树袋熊长得一点都不像
but neither they nor the sloths look like the koala,
他拥有澳洲所特有的魅力
which has an Australian charm all of its own.
我们对树袋熊的表亲，袋熊所知甚少
The wombat is a much less specialised cousin of the koala's,
他们生活在同一片大♥陆♥
and it lives entirely on the ground.
它同样是素食主义者，但对食物甚少挑剔
It too is a vegetarian, but is very much less selective about what it eats.
如果非得找一个北半球的类似动物
If you had to pick a northern hemisphere version of this creature,
或许就是土拨鼠
it might well be the marmot.
都吃草，挖洞
Both graze, and both dig burrows for themselves.
袋熊有好几个品种
There are several kinds of wombat.
这是另外一种，毛鼻的
This is another, the hairy-nosed.
同样穴居
It too is a burrower,
在现实环境中它们都不是
and neither it nor any wombat is exactly renowned for its darting intelligence
以快速的反应和速度见长
or speed of reaction under distressing circumstances.
袋狸乍看上去更像野兔
Bandicoots look at first sight rather like rabbits,
但是它们其实根本不像
but the parallel here is not really close at all.
野兔吃草，袋狸靠昆虫和肉类为生
Rabbits eat grass, bandicoots insects and meat.
相似点是它们都有如
The similarity between the ears
北美野兔般的大耳朵
and those of long-eared rabbits, like the American jackrabbit,
因为它们都生活在酷热的沙漠地区， 靠大耳朵来散热
is because both live in hot deserts and use their ears for cooling their blood.
这种澳洲蜜负鼠在世界其他地方 根本没有相似的
This Australian, the honey possum, has no close equivalent at all elsewhere.
它靠花蜜为生，用末端有刷子的舌头来收集
It lives on nectar, which it gathers with a tongue that has a brush at the end.
如果你要寻找与它相似的动物
If you wanted to find a parallel for that,
或许就是同样拥有相似舌头的食蜜蝙蝠了
the nearest would be the brush tongue of nectar-feeding bats.
当南方超大♥陆♥裂开的时候
When the southern supercontinent broke up,
澳洲主要为森林所覆盖
Australia was largely covered by forests,
里面仍然生活着非常原始的有袋动物
and those that remain still contain some very primitive marsupials.
这个小东西叫长鼻袋鼠，在它身上你可以发现
This little creature is a potoroo, and in it you can see the beginnings of features
澳洲最著名的有袋动物，袋鼠的最初特征
that characterise the most famous of all the Australian marsupials, the kangaroos.
比如，长鼻袋鼠有跳跃的趋势
For one thing, the potoroo has a tendency to hop.
另外，它的宝宝也偶尔跑回
For another, its young retain the habit
育儿袋喝奶
of popping back to the pouch for a drink of milk
尽管它们已经可以自己觅食
until long after they're able to fend for themselves.
尽管已经长大，他们还是喜爱这种旅行方式
They have a preference for travelling that way even when they're quite large.
在更开阔的森林
In more open woodlands
有一种动物将这两种爱好 发挥得淋漓尽致，小袋鼠
there are animals that have developed these two tendencies further: wallabies.
它们有24种
There are two dozen different kinds of them,
这种被称为小型沙袋鼠
and this one is known as a pademelon.
这种古怪的小袋鼠在南澳洲这个巨大的
This odd wallaby has colonised the huge tropical island just north of Australia,
热带岛屿，新几内亚称王称霸
New Guinea.
这儿其他的动物非常少
Very few animals of any kind live here.
除了它之外还有一种袋鼠
There's this creature and a kangaroo that,
难以置信的是这种以跳跃而闻名的动物
unbelievable it may seem for an animal clearly designed for hopping,
竟然爬上了树
has taken to trees.
树袋鼠看起来是所有树生动物中最笨拙的
The tree kangaroo seems just about the clumsiest climber of all tree-living creatures.
原因是这里是新几内亚
The explanation seems to be that here in New Guinea
他是树上唯一的哺乳动物
it's the only mammal that's got up into the branches.
没有对手和它争夺树叶
With no other creature competing with it for leaves,
似乎没有必要变得更好
it's had no need to become better adapted.
它可以得到所有它想要的
It can get all it wants just as it is.
在澳洲和它附近的岛屿 像新几内亚和毛里塔尼亚一共有
All in all there are over 150 different kinds of marsupial
150多种有袋动物
in Australia and its offshore islands, like New Guinea and Tasmania.
不久以前，这个数目还要更多
But not so long ago, there were even more.
在澳洲的洞穴中可以发现它们存在的壮观迹象
You can see the most spectacular evidence of their existence in Australia's caves.
1969年，一对动物学家夫妇
In 1969 a couple of zoologists
爬下了这个狭窄的石灰石山洞
came crawling down this narrow cavern in the limestone hills of Naracoorte
它位于南澳州离阿德莱德不远的纳拉库特
in South Australia, not far from Adelaide.
他们是首次通过这种方式来到这儿的人类
They were the first people ever to come this way,
他们期待发现一两块骨骸
and they were hoping that they might find a bone or two.
在四分之一英里远的地方的发现
What they discovered, another quarter of a mile farther on,
却远远超乎了他们想象
exceeded their wildest imaginations.
他们发现了在澳洲的洞穴中所发现的最好
They discovered the greatest and most important deposit of bones
最重要的骨骸堆积
ever found in a cave in Australia.
来到这个非凡的通道花了他们一个半小时
It takes an hour and a half of crawling to reach this extraordinary gallery.
远古的河流把数以千计的骨骸冲刷到了这儿
Ancient streams have washed down thousands of bones and left them here.
它们看起来就像几个星期前堆放在这儿的， 如此新鲜
They look so fresh that they might have been deposited only a few weeks back,
但是这些骨头的主人已经灭绝了几千年了
but nearly all belong to kinds of marsupial that have been extinct for thousands of years.
这是一个大袋鼠的头骨
This is a skull of a giant kangaroo
它站起来有9英尺高
that could browse up to a height of about nine feet above the ground,
现存的袋鼠最多也只有它一半高
half as high again as any living kangaroo can do.
它球根状的脸上有一双大大的眼睛
It had a bulbous face with very big eyes
和有力的高齿冠牙齿
and powerful high-crowned teeth,
可以咀嚼坚韧的叶子
with which it could masticate really tough leaves.
你或许把这个当成小犀牛的头骨
You could take this for the skull of a small rhino,
实际上它属于一只有牛般大小的大袋熊
but in fact it belonged to a giant wombat as big as an ox.
牙齿显示它咀嚼粗糙的草木
Its teeth suggest that it chewed coarse vegetation.
洞穴中最奇特的头骨就是这一个
The most extraordinary skull in these caves is this.
它属于一种猎食性的负鼠
It belonged to a creature that was a kind of killer possum.
它以凶猛的有袋动物而知名
It's popularly known as a marsupial lion.
活着的时候，它有美洲虎大小
In life it was about the size of a leopard.
它的四肢更像树袋熊
Its four legs were shaped rather like those of a koala,
除此之外，他的拇指上还有用来撕裂
except that it had on its thumb
食物的利爪
a vicious, hooked claw, with which it ripped apart its prey.
但最奇异的还是它
But the most fantastic thing about it are its teeth.
鄂后部的牙齿
In the back of its jaws
这些专业的牙齿延伸成锋利的刀片
it had these single teeth, elongated to form great shearing blades,
我们确信，由它来把猎物切成碎片
with which, doubtless, it sliced through the flesh of its prey.
或许它从树上跳到大袋鼠的背上 谁知道呢？
Maybe it jumped from trees onto those giant kangaroos. Who knows?
尽管有锋利的牙齿
But despite the formidable armoury of teeth,
这些猎食性有袋动物 还是在1万8千年到2万年前灭绝了
all the marsupial lions became extinct between 20,000 and 18,000 years ago,
大袋鼠同样如此，为什么？
as indeed did all the giant kangaroos. Why?
土著人这时来到了澳洲
Well, aboriginal man had certainly reached Australia by this time,
但没有证据显示这些动物被过度猎杀
but there's no evidence that these creatures were overhunted.
没有，原因似乎是气候产生了变化
No, the reason seems to be that there was a change in the climate,
气候变得越来越干燥
which became extra-dry about this time.
澳洲气候的这种变化
That change in Australia's climate
可以追溯到4千5百万年前
can be traced right back to a time some 45 million years ago
澳洲刚刚和南极洲分开的时候
when the continent first split away from Antarctica.
因为分离后，澳洲并没有静止
Because after the separation, Australia didn't just stay still,
而是继续向北朝赤道漂移
but continued to drift slowly northwards towards the Equator.
至今如此
Indeed, it's still moving in that direction even today,
每年大约移♥动♥5厘米
and as fast as it has ever done, which is about five centimetres a year.
对植被的影响是戏剧性的
The effect on the vegetation has been dramatic.
茂盛凉爽而潮湿的森林
The lush, cool, wet forests
变成干旱的开阔地 像澳洲中部的我周围的这地方
changed into arid open country like this around me in central Australia.
一群有袋动物迅速做出反应
And one group of marsupials were quick to respond to this change.
那儿就有一些
There are some of them just over there.
在这些开阔地，这些类似小袋鼠的有袋动物
Out in this open country, the small wallaby-like marsupials
长得更大，跳得更远更快，变成了袋鼠
grew bigger, hopped farther and faster and became kangaroos,
和它类似的是鹿和羚羊
the marsupial equivalent of deer and antelope.
靠着巨大的后肢和有力的尾巴提供平衡