It is evolutions' most inspiring achievement 进化史上无与伦比的成就
the power of flight 飞行的力量
From insects to birds to bats 昆虫，鸟，蝙蝠
tens of thousands of species fill our skies 成千上万的物种盘旋于天空
But hundreds of millions of years ago 但数亿年前
flight did not exist 飞行并不存在
This is something only occurred four times 在地球的进化史上
in all of the evolutionary history on the planet 飞行的演化只发生过四次
How did these animals come to seemingly 这些动物是如何
defy the laws of gravity? 克服地心引力？
How did they first take flight? 它们是如何首次飞上天空的？
[Music] [ 音乐 ]
The animal kingdom is composed of millions of species 动物王国中有数百万的物种
And the fastest of all of them 其中速度最快的动物
the peregrine falcon 游隼
Reaching speeds of more than two hundred miles per hour 它的速度可以超过约322千米每小时
this bird swoops down from more than 游隼从约805米的高空
half a mile in the sky to attack 俯冲下来进行攻击
with lethal precision 一招致命
The peregrine's tremendous speed and success at hunting 游隼的速度和完美狩猎
can be attributed to one simple trait 这可以归结为一个简单的特质
the power of flight 飞行的力量
While humans always dreamed of flying 虽然飞行是人类的夙愿
Evolutionarily flight has passed us by 人类在进化上已与飞行失之交臂
But incredibly more than three-quarters of all 但难以置信的是超过四分之三的
land animals can take to the air 陆地动物可以飞翔
From butterflies to birds to beatles and bats 从蝴蝶到鸟类 从昆虫到蝙蝠
These vastly different organisms have all 所有构造如此不同的生物
evolved the complex mechanism of 都进化出复杂的机制
getting and staying airborne 飞翔于空中
Flight occurs when an animal has enough lift 飞行是指动物有足够的上升力和冲力
and thrust to move its body through the air 来抬升身体于空中
and to maintain it in the air 并保持飞行的状态
But what forces drove the development of 但是什么力量推动了这一
such a remarkable innovation? 非凡的创造？
When did the first animals take to the air? 飞行的始祖何时展翅高飞 ？
And how did they develop this ability 它们又是如何演化出这种
to seemingly defy the laws of gravity? 看似克服地心引力的能力？
The sparks of this extraordinary evolutionary change 这一非凡的进化迸发的火花
can be seen all around us today 如今也可以在我们身边看到
Insects 昆虫
For millions of millions of years nothing could fly 数亿年来 飞行并不存在
and so if a small invertebrate was moving around 如果小型无脊椎动物
in the forest and wanted to find food had to crawl all the way up to 在森林里寻找食物只能一路爬到树顶
top of a tree and get the food 得到食物
and then go down that tree 然后爬下树
and up another tree to get food 再爬上另一棵树觅食
But then suddenly something happens 但随后突然发生了变化
the first fly organisms appeared 首次出现了会飞的生物
and once flight became part of the game 一旦飞行成了游戏的一部分
it changes everything 一切随之改变
The fosil record shows that insect flight evolved suddenly 化石显示 大约在3.5亿年前
around three hundred and fifty millions years ago 昆虫突然进化出了飞行的能力
Mutations and natural selection produced the first species 突变和自然选择开辟了飞行的先河
with wings capable of lifting them into the air 昆虫的翅膀能够将其抬升到空中
This random evolutionary accident 一百多万种昆虫的骨骼中
can now be seen in the anatomy of more than a million insects 仍可以看到这种随机进化的痕迹
Their wings have evolved to be like 它们的翅膀已经进化成
curved long helicopter blades 形如弯曲的长长直升机桨叶
and the wing surfaces are not flat 翅膀表面并不是平整的
which make them highly maneuverable in tight spaces 使它们在狭小的空间里有较高机动性
so that they can easily find food and escape predators 所以能轻易找到食物和躲避掠食者
Insects are very good at flying 昆虫非常善于飞行
They can hover they can fly quickly 它们能盘旋飞行 快速飞行
they can fly backwards 也可以倒着飞
they can turn very tight turns 可以急转弯
They can go very very high 可以高空飞行
and they've taken advantage of this to 昆虫借此优势
fill all the different niches in the world 占领了世界上的角角落落
Although insects would be the first animals to fly 虽然昆虫是飞行的鼻祖
they would not be the last 它们不会成为唯一
To fly an animal not only has to get up into the air 会飞的动物不仅要上升到空中
but once there 一旦处于空中
take in huge amounts of energy and oxygen 还必须能够消耗大量能量和氧气
to power them through the sky 为飞行提供动力
Considering the physical demands 考虑到生理因素
it's no wonder that the heaviest flying animal today 难怪如今最重的飞行生物是
the great bustard 大鸨
weighs in at mere forty five pounds 体重18千克
If you watch birds in different sizes 如果观察不同大小的鸟类
especially when they try to take off from the ground 特别是当它们想从地面起飞时
the first thing we usually notice is that 首先注意到的是
large birds have trouble getting off the ground 大型鸟类起飞时会遇到麻烦
But one of the world's first flyers 但最早的飞行生物之一
would break all the evolutionary rules about size 将打破所有有关体型的进化规则
The first group of vertebrate flyers would produce 第一批飞行脊椎动物中
the largest flying animal of all time 诞生了迄今为止最大的飞行动物
a 440 pound pterosaur called Quetzalcoatlus 重达约200千克的羽翼蛇龙
This is Quetzalcoatlus 这是羽翼蛇龙
the largest flying animals of all time 迄今为止最大的飞行动物
with wingspan of about thirty-five feet 翼展约11米
This animal soared over western north America 这种动物曾翱翔于北美西部
When in full flight its wingspan was equal to 飞行时翼展相当于
three cars parked bumper to bumper 三辆汽车首尾相连的长度
Imagine that thing coming at you 想象如此庞然大物朝你飞来
The gigantic pterosaur had a huge beak head 这种巨型翼龙的喙
the size of a human 大如成年人的体积
and when standing on the ground 站立在地面上时
was taller than a giraffe 可以俯视长颈鹿
At four times the size of any flying animal today 其体积是如今飞行生物的四倍
it's an anomaly of evolution 这是一个反常进化现象
What ecological pressures drove 是什么样的生态压力
these enormous animals into the sky? 促使这样的庞然大物飞向天空 ？
And how it physically possible? 以及从生理角度它如何能做到这一切？
Weighing hundreds of pounds it seems unlikely 羽翼蛇龙重达数百千克飞行似乎不可能
even its massive wings could have generate 即使它巨大的翅膀能够产生
enough force to drive it into the air 足够的力让它升上天空
Pterosauria live 220 million years ago 翼龙生活在2.2亿年前
and were the first vertebrates to evolve powered flight 并且是第一种进化出飞行能力的脊椎动物
Their name comes from the Greek pterosaur 其名称来自于希腊语 "pterosaur"
meaning winged lizard 含义为有翅膀的蜥蜴
Unlike birds these first vertebrate fliers did not have feathers 与鸟类不同 这些脊椎动物飞行的始祖没有羽毛
but skin that stretched from their pinky fingers 但是从小指延伸出的皮肤
to their backs to form a wing 一直到达背上形成了翅膀
The first vertebrate group to fly 脊椎动物飞行的始祖
to evolved flight were the pterosaurs 是翼龙
They're closely related to dinosaurs but not dinosaurs themselves 它们与恐龙密切相关 但不是恐龙
The world of the pterosaur was a 翼龙生活的世界
strikingly different place than today 和如今的世界截然不同
Dinosaurs tower above the canopy 恐龙高如树冠
while down below millions of insects buzz around their feet 脚下围绕着无数的昆虫
along with hundreds of species of reptiles 和许多的爬行动物
all competing for resources and food 都在争夺资源和食物
The ability to fly opened up 飞行的能力为翼龙带来了
numerous new ecological possibilities for pterosaurs 许多新的生态可能性
One of the earliest ones was probably 其中最早的是
the ability to catch flying insects on the wing 能捕获飞行昆虫
So these guys could fly pursue flying insects 所以这些翼龙能够追捕会飞的昆虫
grab them and eat them 抓住并吃掉它们
Pterosaurs also look to oceans and lakes 翼龙的目光也投向海洋和湖泊
as a source of food 那里也是食物的来源地
They fly over the water swooping down for fish 它们盘旋在水面上 然后俯冲下来猎鱼
Being in the air also gives them a better vantage point 飞行在空中给它们一个更好的视野
for spotting dead animals to scavenge 能够找出死尸满足食腐的需求
New food resources explain the desire 新的食物来源解释了
for wanting to get up into the skies 它们飞向天空的欲望
But just how did these 440 pound behemoth get there? 但这些200千克重的庞然大物是如何飞上天的呢？
How an animal this big got off 体型如此之大的动物是如何
the ground and stayed into the air has 离开地面飞到空中
been a puzzle ever since its discovery 这是从翼龙发现以来一直存在的谜题
Michael Habib is an evolutionary biologist 进化生物学家Michael Habib
at Johns Hopkins University 授教于约翰霍普金斯大学
He thinks he solved the mystery of 他认为自己解决了
how these monstrous reptiles conquered flight 这些可怕的爬行动物是如何征服飞行的谜题
In the late 1920s 上世纪20年代末
a group of paleontologists unearthed 一群古生物学家在俄勒冈州
a pterosaur skeleton on a dig in Oregon 挖掘出了一幅翼龙的骨架
Included in the skeleton was 在该骨架中
a seemingly ordinary bone from the wing 有一块看似普通的翼骨
The bone was dismissed as insignificant 该骨头被认为无关紧要
and placed in a drawer at a museum for more than 80 years 一直在博物馆的抽屉中存放了80多年
But Habib believes this simple bone from the wing 但是Habib认为这块简单的翼骨
may hold the answer to these massive creatures 也许能解开这些庞大生物
to these massive creatures taking to the air 翱翔于天空的谜题
The bone in question that was found 这块被重新发现的骨头
is the most important part of the wing 是了解翼龙飞行奥秘的
for understanding the flight of pterosaurs 最重要部分
The part that basically connects the wing itself to the body 这块骨头主要连接翅膀和躯干
Toward most was the flight most attached 这是飞行最重要的关节
When I talked to the curators of museum about the pterosaur collection 我和博物馆策展人讨论翼龙馆藏时
It was in fact the last thing they showed me 实际上这骨头被忽视了
It was almost an afterthought 几乎是事后才想起来
They have forgotten it was there 他们忘记了它的存在
The bone was incredibly well preserved 这块骨头保存完好
And Habib sensed he may be onto something Habib感觉到自己在接近真相
Here in front of him could be the part of the anatomy 在他前面的这块骨头
that might just explain how an animal 也许能解释像翼龙这样
four times larger than anything else flying on earth 体积是世上任何飞行动物四倍的生物
could generate enough force 如何能产生足够的力
to get up into the air and stay there 让它们飞上天空并且翱翔其中
Habib wanted to capture high-tech x-ray images Habib想在约翰霍普金斯大学医学院
of the interior of the fossil 获得化石内部的
at the Johns Hopkins University School of Medicine 高科技X射线图像
The first thing Habib noted was Habib首先注意到的是
something paleontologists have long known about the pterosaurs bones 一些古生物学家早就知晓有关翼龙骨骼的信息
They were hollow 这些骨头都是中空的
Hollowness is supposed to be very very large 骨头的空隙非常非常大
and the diameters can be very wide which makes them very strong 骨头的直径也非常宽 所以骨头很强壮
since they could put a lot of muscle power on them 因此这些骨头能承受大量的肌肉力量
and the bone will hold up 并且骨头不会崩坏
This bone however was not completely hollow 然而这块骨头并不是完全中空的
Habib noticed some strange grills inside the bone Habib注意到骨头内部一些奇怪的网状物
It looked like support beams 看起来像支持梁
similar to flying buttresses on a cathedral 类似于教堂中的飞扶壁
that keep the walls from buckling inwards 飞扶壁防止墙壁从内侧屈曲
Their range in particular directions 它们按特定的方向排列
in the direction shows you where the bone 这些排列的方向表明
needed the most reinforced 哪里的骨头最需要加强
where it needed the biggest push on the inside keep it from collapsing 需要最大的推力防止内部塌陷
With this discovery Habib was able to figure out 这一发现使得Habib能够弄清楚
what this bone was used for 这种骨头的用途
It was used to help launch pterosaurs 它是用来帮助翼龙起飞的
like the 440 pound Quetzalcoatlus off the ground 200千克重的羽翼蛇龙起飞离开地面
much like a diver pushing off a springboard 就像潜水员蹬离跳板
Launching is actually very rigorous very difficult for flying animals 起飞实际上对飞行生物是严苛而又困难的
In the sense that they have to get a lot of speed 因为它们需要在很短的时间内
built up in a very short period of time 积蓄很快的速度
To launch off the ground and into air 为了飞离地面来到空中
an animal has to generate a lot of force 动物需要产生很大的力
which takes a lot of muscle power 这需要大量的肌肉力量
In birds you see this most in the hind legs 鸟类双脚能释放大量力量
because for birds actually not the wings 因为实际对于鸟来说
that most get the bird off the ground 翅膀不是起飞的关键
Actually it's the legs 实际上是它们的脚
Legs give the initial leap 脚最初的一跳
starts them into the air 使鸟飞向空中
The discovery of the internal brace system suggests that 内部支撑系统的发现表明
these front limbs were strong enough to 这些前肢已经强大到足以
push the pterosaur up off the ground 将翼龙推离地面
and propel its huge body into the air 并为其巨大的身体提供飞行动力
So their wings were more than just agents of flight 所以翼龙的翅膀不仅起到飞行的作用
they were actually front legs 实际上还有前脚的作用
that they used to walk around on 在地面上翼龙用其走路
and help them push off and into the air 并帮助它们飞向空中
Habib's discovery may go a long way to Habib的发现可能还有很长的路要走
answering some of the lingering debate 这是一场一旷日持久的争论
about how these large first vertebrate flyers got airbone 关于脊椎动物的飞行始祖是如何飞向天空
but the question remains 这个问题一直悬而未决
Why is there nothing this big flying today? 为什么如今没有再出现巨型飞行生物？
The answer may be the size of itself of these animals 答案可能是这些动物的体积
Large animals need more food to sustain themselves 大型动物需要更多的食物来维持生存
And in times of environmental distress catastrophe 在自然环境的压力和灾难下
animals like this this 35 foot wingspan pterosaur 像翼龙这种翼展达11米的动物
would have had a much harder time feeding itself 比体积是其几分之一的鸟类
than a bird a fraction of its size 更难喂饱自己
Their size may have eventually led to their extinction 翼龙的体积最终导致其灭绝
but a hundred and fifty million years ago 但1.5亿年前
another group of animals was independently evolving the ability to fly 另一种动物也独立进化出飞行的能力
alongside the pterosaurs with different flight strategies 它们采取与翼龙不同的飞行策略
naturally selected for their size and anatomy 一种自然选择下适合其体积和骨骼的方式
Interestingly small bird make up 有趣的是小型鸟类
more than half the species of birds in the world 占了鸟类世界的半壁江山
so in the evolution of birds 所以在鸟类的进化中
small birds have arguably been much more successful 小型鸟类比大型鸟类
than their larger counterparts 更加成功
The birds inspiration 鸟类进化的启示
not the flying pterosaurs 不是来自飞行的翼龙
but flightless killers on the ground 而是来源于地面行动的杀手恐龙
A 150 million years ago 约1.5 亿年前
during the mid Jurassic period 在侏罗纪中期
life is teeming with new species 世界上充满了各种新物种
not only on the ground but also far above in the skys 不仅在地面 还有远在云端的
Two separate evolutions of powered flight 两种独立演化的飞行能力
have given rise to millions of species of insects 造就了数百万种昆虫
and pterosaurs have been soaring high above the canopy 和翱翔于空中的翼龙
for over a hundred million years 这一状况持续了一亿年
but they were no longer alone 但它们不再孤独
A new class of creatures was evolving independently alongside them 一种新的生物独立演化了出飞行能力
that would take flight to new heights 将飞行带到了新的高度
Convergent evolution is a phenomenon 趋同进化现象是指
where organisms from two different ancestries 来自两种祖先的生物
evolved similar characteristics 演变出相似的特征
in response to similar environmental pressures 来应对类似的环境压力
and the evolution of flight is an excellent exmple of convergent evolution 飞行的进化是一个极好趋同进化的例子
Birds and pterosaurs both evolved similar body plans 翼龙和鸟类都进化出相似的身体构造
in response to the need to fly more efficiently 来更高效地进行飞行
From pigeon to peacock eagle to sparrow 从鸽子到孔雀 从老鹰到麻雀
today there are over 10,000 species of birds on the planet 今天地球上有超过一万种的鸟类
twice as many as mammals 是哺乳动物的两倍
Exactly when they evolved and how they adapted flight 它们究竟何时进化以及如何适应飞行
is a 230 million year old detective story 是一个2.3亿年古老的谜案
but if you know where to look 但如果你知道方法
there are telltale clues 这里有几条明显的线索
Hey how's it going? 嗨 你们好
Ironically the answer to how birds took to the air 难以想象的是鸟类飞向天空的答案
may lie on the ground 可能在地面上
Large flightless birds like emus 大型鸟类比如不会飞的鸸鹋
help trace the origin of avian flight 能追溯鸟类飞行的起源
because it is believed that birds 这是因为人们认为鸟类
evolved not from winged pterosaurs 不是从有翅的翼龙进化而来
but ground-dwelling dinosaurs 而是从居住在地面的恐龙进化而来
This animal the emu is one of the closest things left on earth 鸸鹋是地球现存最接近答案的生物
that might be able to tell us 能够告诉我们
what non-avian dinosaurs really looked and acted like 那些没有飞行能力的恐龙的外貌和行动特征
For instance look at the feet of an emu 例如看一下鸸鹋的脚
we see scales on the feet like a reptile 有类似爬行动物脚上的鳞片
and also three weight-bearing toes 还有三个负重脚趾
like a non-aviandinosaur 就像没有飞行能力的兽脚类恐龙
Theropod dinosaurs stood upright with hind legs 兽脚类恐龙用后肢直立行走
used for support and movement 后肢用于支撑和移动
while short four limbs were used for 较短的四肢用于
grasping and tearing prey 抓捕并撕开猎物
The most famous was the fearsome Trex 最著名的是令人胆寒的霸王龙
If we were to look at the foot of a Trex 如果我们看看霸王龙的脚
and put a Trex foot next to the foot of this emu 把霸王龙的脚和鸸鹋做对比
you see many many similarities 你可以看到很多相似之处
and only a few differences 只有很少的区别
I think the most obvious feature that birds share with non-avian dinosaurs 我觉得这两者最明显的相同特征
a feature they inherited from non-avian dinosaurs is their feathers 是鸟类继承了兽脚恐龙的羽毛
Feathers were long thought to be exclusive to 在脊椎动物中羽毛一直被认为
birds among vertebrate animals 是鸟类独一无二的特征
but this was not the case 但事实并非如此
Millions of years ago some non flying vertebrates had feathers too 数百万年前 一些非飞行脊椎动物也有羽毛
so we know that feathers are not unique to birds 所以我们知道 羽毛不是鸟类独有的
Feathers first evolved in non-avian dinosaurs 羽毛最初在非飞行恐龙中进化出来
and it's quite possible they evolved for something other than flight 很有可能它们进化出羽毛不单是因为飞行
possibly insulation 可能隔绝的地理
possibly breeding their nests 也有可能是为了孵巢
but aside from sharing feathers 但除了类似的羽毛
how do we know that birds evolved from dinosaurs? 我们怎么知道鸟类是从恐龙进化而来的？
And how were these land-based animals able to take to the skies？ 这些陆地动物如何能飞向天空？
over the last 200 million years？ 在过去2亿年间
paleontologists have begun to find amazing evidence 古生物学家发现了惊人的证据
that helps to answer these evolutionary mysteries 有助于解开这些进化之谜
in the form of incredibly preserved fossils 这些证据就是保存完好的化石
Pittsburgh's Carnegie Museum of Natural History 匹兹堡的卡内基自然历史博物馆
houses one of the world's top collections of dinosaur bones 拥有世界上顶级的恐龙骨骼馆藏
Among them are striking clues of 其中有关于鸟类和鸟类飞行如何从
how birds and subsequently bird flight evolved from dinosaurs 恐龙进化而来的惊人线索
This is a cast of archaeopteryx 这是一个始祖鸟的铸型
and when this was discovered well over a century ago 在一个世纪前发掘出来后
it astounded scientists 它震惊了科学家
because the fossil shows a mixture of features 因为化石显示了混合物种的特征
classically associated with reptiles 一半与爬行动物有关
and classically associated with birds 一半与鸟类有关
Archeopteryx was the first of a whole new group of animals 始祖鸟是一个全新物种的开辟者
It was a bird distinguished from a feathered dinosaur 这是一只与羽翼恐龙不同的鸟类
by its ability to fly 因为它会飞
Even though it may not have been very proficient in the air 尽管它可能不会熟练飞行
there were clear differences in the anatomical structure of this creature 它与不会飞的恐龙在骨骼结构上
compared to non flying dinosaurs 还是有明显差异
As the world's oldest known bird however 作为世界上最古老的鸟类
it naturally had not completely evolved away from its ancestors 始祖鸟却还保留有祖先的特征
Archaeopteryx when we look at its skeleton 观察始祖鸟的骨架可以发现
it shows many features that are retained from dinosaur ancestors 它具有许多来自恐龙祖先的特征
that are lost in modern Birds 在现代鸟类中是缺失的
So for instance if we look at the skull of Archaeopteryx 例如如果观察始祖鸟的头骨
we see that it retains tiny teeth 它保留了细小的牙齿
All known birds alive today lack teeth 目前已知的鸟类没有牙齿
We also see a long bony tail in Archaeopteryx 我们还看到一个长的骨质尾巴
a dinosaurian feature 这是恐龙的特征
We look at the hand of Archaeopteryx 观察始祖鸟的手
we can see that its fingers are still 我们可以看到它的手指
tipped with large curved claws 仍带有较大的弯曲爪子
and this is a feature that dinosaurs have as well 这也是恐龙的特征
In addition Archaeopteryx also seem to 此外始祖鸟似乎也
be missing something else crucial muscles 缺少一些关键的组织
Muscle 肌肉
Modern birds have a series of large pectoral muscles 现代鸟类拥有一系列强壮的胸肌
that attach to their sternum 胸肌附着于胸骨上
and help them generate enough force to fly 有助于鸟类产生足够的力来飞翔
Archaeopteryx didn't appear to have these musles 始祖鸟似乎并没有这些肌肉
So while their bodies can support some flight 所以尽管它们的身体能够支持飞行
it is unlikely they could stay airborne for very long periods of time 但不能长时间停留在空中
Archaeopteryx probably could fly 始祖鸟可能会飞
but compared to modern Birds 但相较于现代鸟类
was almost certainly very clumsy 几乎是很笨拙的
we know this because its skeleton is much more primitive 因为它的骨架比现代鸟类的
primitive than that of modern birds 更原始
So how did modern birds evolved to become more efficient fliers? 现代鸟类是如何进化成更加出色的飞行者？
What was the next evolutionary step after Archaeopteryx? 始祖鸟之后 进化的下一步是什么？
[Music] [ 音乐 ]
In 2004 on a dig in northwestern China 2004年在中国西北部
Lamanna and his colleagues came across Lamanna和他的同事偶然发现
another fossilized piece to the puzzle 另一块解开谜题的化石
The more I looked it became clearer that 越观察我越清楚
we were looking at a very bizarre group of birds 这是一个非常奇特的鸟类种群
that were abundant during the Cretaceous period 它们繁盛于白垩纪时期
the final period of the age of dinosaurs 恐龙存活的最后时期
Close to a hundred nearly complete skeletons 近百副几乎完整的鸟类骨架
of a hundred million year old birds 跨越了上亿年的时光
birds were recovered on the dig 最后在这个地点被挖掘出来
Among them a rare specimen 其中有一件珍贵的样品
Tiny fragments of this long extinct animal 甘肃鸟早已灭绝
called Gansus had been found before 以前发掘过它们的细小碎片
but never a skeleton as complete as this one 但是没有发现过一个完整的骨架
Gansus dates to 40 million years 甘肃鸟可追溯至4000万年前
younger than Archaeopteryx about a hundred and ten million years ago 而始祖鸟生活于约1.1亿年前
and already relatively rapidly in bird evolutionary history 在鸟类快速的进化史上
Gansus has acquired many of the features that we associate with modern birds 甘肃鸟已具有许多和现代鸟类相关的特征
It's in many ways an anatomically of modern bird 从骨骼上来看这只1.1亿年前的鸟
from a hundred and ten million years ago 在很多方面与现代鸟类相似
Although Archaeopteryx was capable of flight 虽然始祖鸟能够飞行
Lamanna would soon discover that Ganz's had anatomical features Lamanna很快发现甘肃鸟拥有一些骨骼特征
that almost certainly made it a far better flier 使它的飞行能力更加出色
A lot of the story of the evolutionary history of birds 很多关于鸟类演化的历史
has to do with the increased efficiency of flight 都与增加飞行效率有关
So for instance when we look at Archaeopteryx 例如当研究始祖鸟
we see features that are not present in modern birds 我们关注现代鸟类不具备的特征
such as teeth and a long bony tail 如牙齿及长而多骨的尾巴
These are two features that have long been argued to 人们一直认为这两个特征
have been lost in modern birds 不存在于现代鸟类中
because they saved weight 处于减轻重量的目的
Loss of teeth a shorter tail and other distinguishing features 无牙 较短的尾巴和其他特征
make Gansus an intermediate animal 使得甘肃鸟成为一种过度生物
between the largely dinosaurian Archaeopteryx on one side 一边是类恐龙的始祖鸟
and modern Birds on the other 另一边是现代鸟类
But the fossil have the pectoral muscles 但这块甘肃鸟的化石有胸肌
that could help it get airborne more easily than Archaeopteryx? 这使它比始祖鸟更容易飞升于空中吗？
Trouble was although the Gansus's fossil was complete 问题是尽管甘肃鸟的化石是完整的
it was also badly flattened 但它扁的不成形
making it nearly impossible to 几乎不可能
see the certain anatomical features of this new species 看到这个新物种的骨骼特征
Would critical questions to this mystery go unanswered? 这个谜题的关键会悬而未决吗？
Fortunately Lamanna is able to turn to 幸运的是Lamanna向
a team of paleo sculptors and artists 卡内基自然历史博物馆
at the Carnegie Museum of Natural History 一个艺术家和雕塑家团队求助
to try and recreate the image of this ancient bird 来重建这种古代鸟类的图像
Working like crime-scene investigators 他们的工作像犯罪现场调查员
the team is able to methodically reconstruct the crushed bones 该团队能够有条理地重塑骨骼碎片
and create a picture of what Gansus's would have looked like 创建出甘肃鸟外观的图片
As Lamanna had hoped 正如Lamanna所期望的
Gansus appeared to have a body capable of supporting large strong wings 甘肃鸟似乎拥有支撑强壮大型翅膀的躯体
The presence of a bony sternum on Gansus's means 甘肃鸟的较大胸骨意味着
that this creature would have most likely had larger pictoral muscles 相比胸骨较小的始祖鸟
compared to the relatively puny ones seen on Archaeopteryx 该生物很有可能拥有大块胸肌
Today all flying birds have large muscles 如今所有的飞行鸟类拥有
similar to those found in Gansus's 和甘肃鸟类似的大块胸肌
This provides them with the strength needed to 这为它们提供了需要
flap their wings and get airborne 拍打翅膀和升空的力量
Could Gansus have been the evolutionary step to 甘肃鸟是鸟类成为出色飞行家
allowing birds to become more proficient fliers? 进化历史上的一个阶段吗？
Just got what it has pretty big pecs you know able to flap arms 甘肃鸟拥有较大的胸肌
with quite a bit of force 能够用力拍打翅膀
is probably this pretty good flier 让它有可能成为出色的飞行家
The large breastbone that strong flight muscles 在甘肃鸟身上能清楚看到
could attach to is clearly seen in Gansus 强壮胸肌所附着的胸骨
as well as fused wrist and hand bones a short bony tail 还有腕关节 手骨和多骨质的短尾巴
and fused ankle and foot bones are also traits in most modern birds 融合的踝和足骨也是现代鸟类的特征
All these features transform these early fliers 所有这些特征使得早期的飞行者
from a reptile that could get airborne 从能飞行的爬行动物
to a radical new lineage 演化出完全新的物种
that would spend the majority of its time in the air 鸟类大部分时间在空中度过
Gansus was probably an excellent flyer 甘肃鸟可能是出色的飞行家
probably as good a flyer as are many types of modern birds 不亚于许多现代鸟类
Birds are one of the most successful groups of vertebrates 鸟类是最成功的脊椎动物之一
but in order to survive in a new environment 但为了适应新环境
major anatomical changes had to be made 鸟类的骨骼发生了巨大的变化
What was useful on the ground 适用于陆地的构造
would hold them back in the sky 会阻碍它们在天上的飞行
When birds gained the ability to fly from dinosaurs 鸟类从恐龙演化出飞行的能力
it came with some costs 但也付出了代价
They had to lose a few things 鸟类不得失去一些东西
The most obvious of which is probably 最明显的可能是
that they don't have anymore hands 鸟类不再有手
All the bones of the fingers are now incorporated in the wing 所有的指骨演化成了翅膀的一部分
and there are feathers attached to them 上面布满羽毛
So they can no longer manipulate anything with their hands 这样鸟类就不能用手操控
or defend themselves on the ground 或者在地面上进行防御
Regardless of this cost however the fossil record clearly shows 尽管如此 但是化石清楚地显示
that the evolutionary transition from dinosaurs to birds 从恐龙向鸟类的进化
was a great triumph 是一个巨大的胜利
and over time birds radiate far and wide 随着时间 鸟类飞得更高更远
[Music] [ 音乐 ]
These groups that involve the ability to fly 这些进化出飞行能力
and diversified into hundreds or thousands of species 并演化出数十万物种的群体
have gone on to fill many different niches of the environment 已经占据了自然的角角落落
Incredible fossils like Archaeopteryx and Gansus 始祖鸟和甘肃鸟神奇的化石
help us to understand what anatomical features 有助于了解鸟类骨骼特征
define a bird and when they evolved 并弄清骨骼进化的时间点
but what were the environmental factors that 但是什么环境因素把
send birds into the air? 鸟类推向天空？
When we're trying to examine the origin of flight of bird flight 在试图探讨鸟类飞行的起源前
we need to answer a couple of questions 我们需要回答几个问题
and perhaps the biggest one is 其中最关键的问题是
what were the selective forces thrusting birds into the air? 什么样的自然选择使得鸟类能振翅高飞？
What was happening down on the ground 在地面上发生了什么
that turned two footed feathered dinosaurs into masters of the skys? 使得双足带羽恐龙成为天空的主人？
Through the fossil record we know that 通过化石记录我们知道
birds that were capable of flight 鸟类从恐龙进化而来
evolved from dinosaurs 并在1.4亿年前
over a hundred and forty million years ago 进化出飞行的能力
but the biggest mystery of all still remains 但最关键的谜题没有解开
What forces would have driven land-based creatures to take to the skies? 是什么力量驱使陆地生物飞向天空？
When somebody asks what was the behavior of a fossil 当有人问什么是化石行为
of course we're reaching in to an area of speculations at least 那么至少涉及到推测的方式
How do we explain each of the transitional stages 我们如何解释从恐龙到鸟类时代
from the birds dinosaur history to today? 的每一个过渡阶段？
Ken Dial professor of biology at the University of Montana Ken Dial是蒙大拿大学生物学教授
thinks the answer of how flight first evolved lies 他认为飞行第一次进化的答案
not in the bones of long dead animals 不在那些早就灭绝的动物尸骨上
but in the behavioral patterns of those that are living 而是在如今动物的行为模式上
What we're trying to do is 我们正在尝试
we're trying to borrow from the present 借用现在动物的行为模式
to try to interpret the potential behaviors of the fossil creatures 来解释化石生物的潜在行为
Dial and his colleague Brandon Jackson run Dial和他的同事Brandon Jackson经营
an avian Flight Research Center 一家鸟类飞行研究中心
in the foothills of Montana 该中心位于蒙大山脚下
Their work focuses on uncovering the origins of bird flight 他们的工作主要是揭开鸟类飞行的起源
Why do birds need to fly ? 为什么鸟儿需要飞？
Why do they want to fly? 它们为什么要飞？
Dial believes that birds evolved the power to fly slowly Dial认为鸟进化出飞行能力是个缓慢的过程
Over time environmental pressures like escaping predators 如逃避捕食者这样的环境压力
push them towards the sky 久而久之使鸟类飞向天空
and various physical adaptations allowed them to get there 各种身体的改造使它们能够飞翔于空中
If this is true claims dial 如果这种说法是正确的
many birds may still be hardwired with the 许多鸟类身体内部
behavior of their land dwelling ancestors inside 仍然留有陆地祖先的行为印记
In other words if given the choice between using their wings or their feet 换句话说 如果在翅膀和脚之间选择
birds will choose to remain on the ground 鸟类会选择留在地面上
To test their hypothesis 为了验证他们的假设
Dial and Jacks have put birds in a position to have to choose between Dial和Jackson让鸟类处于一个情景中
flying and keeping their feet earthbound 必须在飞行和立足于地面中做选择
They take birds that are fully able to fly 实验对象是具有完全飞行能力的鸟
and place them at the foot of a ramp with a steep incline 将它们放在陡坡下
There we go 可以开始了
What they observe is that 我们观察到
these birds choose to run keeping both feet grounded 这些鸟类选择脚着地的方式奔跑
rather than fly to the top of the ramp 而不是飞到斜坡的顶部
Changing the steepness of the ramp does not alter the result 改变斜坡的陡度结果不变
Starting with a 30 degree incline then 60 75 and finally 90 从30°倾斜开始 然后60° 75° 最后 90°
Each time the bird chooses to run instead of fly 每次鸟儿都选择奔跑而不是飞行
When we look at the angle which they're trying to scale 如果观察鸟类尝试爬升的坡度
we've come to learn something very very special 我们注意到一些极其特殊的现象
and that is if a bird is trying to ascend something 如果一只鸟试图爬上
that is less than 60 degrees 坡度小于60°的物体
they can do so easily just with their hind limbs 它们很容易就能用后肢做到
and with their wings tucked to their side 同时翅膀是收于两侧
but as soon as they start to scale anything higher than about 60 degrees 但一旦角度开始超过60°
you'll automatically see the wings jump in to the whole process 鸟儿在整个过程会边跑边扇动翅膀
Dile has termed this behavior "wing assisted inclined running" Dial称这种行为“翅膀辅助斜道跑”
At these steeper inclines 在越陡的坡上
the birds flapping wings provide additional power 鸟类拍动翅膀获得额外的动力
to support the hind limbs 来支撑后肢
and assist in keeping the bird's body from falling down the ramp 并有助于防止身体掉下斜坡
Instead of making a big jump from running on the ground to flying 没有选择直接从地面起飞
running up inclines with the wings assisting their legs 而是边跑边挥翅膀辅助脚
provides small incremental evolutionary adaptive stages 这是一个循序渐进的适应过程
for the birds to slowly grow larger and larger wings 鸟的翅膀慢慢越来越大
and more powerful flight apparatus 也有更强大的飞行机能
At a 90 degree angle the wing beat frequency and force 在90°时翼振的频率和力度
produced approaches that needed for flight 提供了飞行所需的能量
So if we were to take a bird running 所以如果我们研究
on a 90 degree ramp a vertical ramp 在90°垂直斜坡奔跑的鸟
and then take the ramp away 然后把斜坡拿掉
the bird would not have to change a thing 鸟儿不会有任何改变
It wouldn't have to change its wing stroke angle 它不会改变翅膀挥动的角度
and wouldn't have to change its wing beat frequency 也不会改变其翅膀扇动频率
and it would be fly 这就是飞行
Could the desire to keep their feet on solid ground 双脚触地而不是起飞的欲望
instead of flying be a remnant of their evolutionary past? 是鸟类进化的残留印记吗？
We think that they have this ingrained in their neurocircuitry 我们认为这种意识植根于它们的神经机制
that if their feet are touching the ramp 鸟类的双脚一旦接触斜坡
they have to run up 就不得不向上跑
It is possible that they stayed earthbound 鸟类也有可能呆在陆地上
because for the millions of years before they could fly 因为数百万年前 其恐龙祖先还不会飞的时候
their dinosaur ancestors were land dwellers 它们也是陆地生物
Dial and Jackson hope to get a clue Dial和Jackson希望找到
as to how it ingrain in behaviors in birds 关于这种行为的
They conduct the experiment again 他们再次进行试验
This time using baby chicks that haven't yet learned to fly 这次他们选取还没有学会飞的幼鸟
The result the same as with the adult flying pigeons 结果与成年鸽子一样
The baby chicks run up the ramp 幼鸟跑上斜坡
and as the incline gets steeper 随着斜坡变陡
they flap their little wings harder and faster 它们用力快速拍打小翅膀
Jackson believes that this behavior Jackson认为这一行为
can explain the evolutionary steps 可以解释这一进化步骤
that the dinosaur ancestors of birds 鸟类的恐龙祖先
those without fully formed wings 它们还没有完全成形的翅膀
may have taken to develop the adaptations needed for true flight 已经演化出可适应真正飞行的机能
Over millions of years most likely 很有可能在过去数百万年间
theropod dinosaurs went from running on level ground 兽脚类恐龙从平地奔跑
to running up shallow inclines 到在稍陡的斜坡奔跑
and when they hit 60 degrees 当坡度达到60°时
they had to start using their pre-wings 它们已经开始使用翅膀的前身
They're flightless little fore arms 没有飞行能力的短小前臂
Now over millions more years 几百万年后
they move from being able to run up 60 degrees 它们从能够爬上 60 °
to being able to run up 70 degrees 变成爬上70°
and then 80 degrees 然后80°
and then finally vertical 最终垂直的坡度
The incremental steps over many millions of years 在几百万年循序渐进中
produce bigger wings stronger muscles 演化出了巨大的翅膀和强壮的肌肉
and more fine-tuning of the wing stroke 以及更加精准的翅膀挥动
which natural selection acts on 这都是自然选择的作用
And bird flight evolves 鸟类进化出了飞行能力
What were the selective forces driving birds to develop a full wing 是什么自然选择力量驱使鸟类进化出翅膀
and the ability to produce significant aerodynamic forces? 并能产生重要的空气动力？
One of the strongest selective pressures out there 其中最重要的自然选择因素是
is the risk of predation 被捕食的风险
The ancestors of birds were small bipedal theropod dinosaurs 鸟类的祖先是小型双足兽脚类恐龙
They only use their hind limbs for moving 它们仅使用后肢移动
To avoid predation they could try and outrun a predator 为了躲避天敌可以跑得比捕食者更快
or they could run up obstacles to get away 或者可以跑上障碍物
By gaining some kind of elevated refuge 通过高空避难所
they are safe 它们一直很安全
Over time the chase between predator and prey grew more intense 捕食者和猎物之间的追逐较量愈演愈烈
and to get away these small theropods had to develop the ability 这些小型兽脚恐龙为了逃脱捕食者
to run up steeper and steeper inclines to escape 跑上越来越陡的斜坡
until they had the power needed for flight 直到它们拥有飞行所需的能力
Once in the air away from the Predators below 一旦到空中远离地面的掠食者
birds could also take advantage of other benefits 鸟类也可以利用其他优势
such as more diverse and readily available food sources 比如更多样化且容易获得的食物来源
Flight allows birds to exploit niches 飞行使得鸟类能够获得
that non flying animals cannot exploit 非飞行动物不能得到的优势
The ability to soar over a prairie in hunt for small rodents 在草原上空翱翔猎食小型啮齿动物
like hawks and eagles do 比如鹰和隼那样
is only available as a niche to flying animals 只有飞行动物才能做到
Dial's experiment may have Dial的实验有可能
finally proven how and why birds first took to the sky 最终证明鸟类飞上天空的原因和方法
but how did they defy the laws of gravity and stay up there? 但它们如何克服地心引力并翱翔天空？
Once birds had evolved and taken to the skies 自从鸟类进化出来并飞翔于天空
the question still remains 这个问题悬而未决
How do they seemingly defy the laws of gravity and stay up there? 它们如何克服地心引力并翱翔天空？
The simple answer would seem to suggest by flapping their wings 简单来说似乎只是通过拍打它们的翅膀
but the evolutionary process that allowed birds to successfully take to the skies 但使得鸟类能成功飞行的进化过程
would require several unique physical adaptations 需要一些独特的生理适应进化
Insects the first animals to fly are very lightweight 飞行的鼻祖昆虫体重非常的轻
and so don't really require much energy to stay airborne 因此不需要太多能量来维持飞行
and unlike birds they don't stay in the air for prolonged amounts of time 与鸟类不同昆虫在空中停留的时间更长
[Music] [ 音乐 ]
Vertebrate fliers like birds are bigger 类似鸟类的飞行脊椎动物要更大
and need huge amounts of energy 并且需要大量的能量
to be able to produce the aerodynamic forces 来产生前进所需的
needed to propel them forward 飞行动力
The primary engine to produce these forces for birds are their wings 翅膀是鸟类前行的主发动机
In an airplane you have a engine and a wing 一架飞机有机翼和发动机
and the engine produces forces to overcome drag 发动机会产生动力以克服阻力
and the wing produces forces to overcome gravity 机翼产生的力克服重力
but in a bird the wing produces both thrust and lift 但鸟类的翅膀同时产生升力和推力
Evolutionarily birds have perfect physical features for life in the skies 鸟类有演化完善适应飞行的生理特征
Their wing is naturally curved on the top 它们的翅膀在顶端自然弯曲
and relatively flat underneath 下面相对平坦
Lift is created by faster air flowing over the top 上方快速流动的空气产生升力
causing it to be pulled up 拉动翅膀
as well as increased pressure pushing against the bottom of the wing 下方压力增加推动翅膀底部
and when they flap their wings 拍打翅膀时
they generate enough force to propel themselves through the sky 产生足够的力推动它们飞向天空
and not just glide 并不只是滑翔
As far as we know 据我们所知
birds produce all of their aerodynamic forces and the downstroke 鸟类产生所有的空气动力和下划力
so they move their wing from above their body 所以它们从身体上方挥动翅膀
using the pectoralis muscle drive the wing down 使用胸肌带动翅膀往下
that produces all of the lift and all the thrust 这产生所有的的升力和推力
95% of the power required for this downstroke 下划力所需95%的动力
comes from a single muscle 来自于一块肌肉
the pectoral muscle 胸肌
On average about one fifth of a bird's body mass 这块为飞行提供动力的肌肉
is devoted to this main muscle that powers flight 平均占到鸟类体重的约20%
As this muscle evolved to get larger over time 胸肌随着时间变得越来越大
it was able to create even more energy 能创造更多的能量
and make birds even better fliers 使鸟儿成为更杰出的飞行家
Also crucial to bird flight is orientation 对鸟类飞行同样重要的还有定向
Birds have the unique ability 鸟类具有这一独特的能力
to always tell what is up and what is down 鸟类在空中飞行时
When they are moving through the air 特别是转向时
especially when they are turning 它们总能分清上下方向
Airplanes have thousands of dollars worth of equipment 飞机上有价值数千美元的设备
to find the horizon 来定位地平线
but birds don't have any of that 但是鸟类没有任何这种设备
instead they have all that in their head in their brain 相反一切都在它们的脑海中
One thing that they have is essentially like an internal gyroscope 它们的大脑中拥有类似陀螺仪的组织
If you take a bird and rotate it 如果你旋转一只鸟的身体
its head stays essentially level 它的头部基本保持水平
This is in stark contrast to most mammals 这种行为与大多数哺乳动物形成鲜明对比
which have a large muscle anchoring their skull to the neck 哺乳动物拥有较大的肌肉连接头骨和颈部
so the head goes where the body goes 因此头部随身体的移动而移动
So when birds turns 所以鸟类转向的时候
they bank their whole bodies 倾斜整个身体
and they have to keep their head perfectly straight 必须保持与头部一条直线
so that they don't lose track of where the ground is 因此不会迷失地面的方向
But it may be another advancement 但也许是鸟类飞行能力中
that has proved the most crucial in birds evolving the power of flight 进化出另一法宝更为至关重要
The key to virtually every land animal success 所有陆地动物成功的关键是
is the ability to process oxygen 消耗氧气的能力
In order to be able to have enough energy for flight 为了能有足够的力量支持飞行
birds have developed a revolutionary use of oxygen 鸟类进化出创造性使用氧气的能力
The problem is that they need 问题就是
to take in huge amounts of energy and oxygen 需要大量的能量和氧气
The secret lies in the birds internal structure 秘密就在于鸟类的内部结构
Birds like pterosaurs have hollow bones 鸟类有翼龙的空心骨骼
that connect to sacks filled with air 连接至空气填充袋
These pneumatic bones are really the footprints 这些气垫骨骼是气囊系统
in the skeleton of an air sac system 在骨架中留下的证据
An air sacs system is there to provide the oxygen that flight requires 气囊系统用以提供飞行所需的氧气
What is an air sac system? 气囊系统是什么 ？
And how does it work? 它如何运作 ？
Vertebrate paleontologist Leon Klassen 脊椎动物古生物学家Leon Klassen
from the College of the Holy Cross 来自圣十字学院
studies this intricate system in various species of bird 他研究不同种类鸟身上的这种复杂系统
Unlike mammalian lungs which expand and contract when you breathe in and out 与哺乳动物在呼吸时可伸缩的肺不同
Lungs in birds are fixed in size 鸟类的肺大小是固定的
They never change in volume 体积保持不变
when fresh oxygen-rich air is inhaled 无论是新鲜的富氧空气吸入时
and used-carbon dioxide rich air is exhaled 还是富含二氧化碳的空气被呼出时
But what a bird has to actually move air around 但实际鸟类在其呼吸系统
in its respiratory system 运输空气的一些列组织
is a whole series of what are called air sacs 就是所谓的气囊
which are balloon-like extensions 它们像气球一样延伸
that hook up to the various airways 连接不同的气管
By juggling air between these various air sacs 通过在不同的气囊之间传输空气
birds are capable of getting a highly efficient air flow through their lungs 鸟类能持续获得储存在气囊中的空气
by continuously extracting oxygen from air stored in the sacs 为肺部提供不间断的氧气来源
both as they breathe in and also when they breathe out 无论是在吸气还是呼气的时候
At Harvard University's Concord Field Station 在哈佛大学康科德调查站
Klassen and his associates Klassen和他的同事
used an x-ray video technique called cineradiography 使用X射线影像技术
to observe how this unique air sac system works 来观察这个独特的气囊系统如何运作
Klassen positions the bird inside the device 他把一只鸟放置于设备中
where the video captures images of the air sacs at work 视频图像捕获气囊的运作图像
You can see right here on this film 在这段影像上可以看到
that as the rib cage 胸腔的动作
The majority of these air sacs 大多数这些气囊
and especially the ones toward the tail end of the animal 尤其是那些在鸟类尾部的
greatly increase in size 体积大大增加
These air sacs allow the animal to 这些气囊能够使得鸟类
continuously shift air around 在需要氧气的时候
as and when they need it 为它们持续提供氧气
And provides them with a highly efficient breathing apparatus 并提供一个高效的呼吸机制
that is unique to birds 是鸟类独一无二的
You see right here with anatomy in action in the living animmal 看这里活鸟的骨骼在活动
One of the most elegant and most efficient designs 这是最优雅最高效的设计之一
that isn't present in any living vertebrate 不存在于任何脊椎动物身上
any living backbone air-breathing animal 任何现存的有脊椎和呼吸系统的动物身上
All living birds today have air sacs 今天所有现存鸟类都有气囊
and there's evidence that they were present in some dinosaurs 也有证据表明一些恐龙也有气囊
So they must have evolved long before birds ever took to the skies 所以气囊在鸟类进化出飞行能力前就已存在
In large dinosaur such as Tyrannosaurus 在大型恐龙如霸王龙中
you have evidence for the presence of air sacs 就有证据证明气囊的存在
because you have openings in the bones 因为它们的骨骼上有开口
where parts of these air sacs has invaded the bones 这表明部分气囊已经侵入骨头
Anatomy that had already evolved in ground running dinosaurs 这一骨骼组织已经在陆地恐龙身上进化出来
like air sac and feathers was fine-tuned 如羽毛一样在自然选择下
by natural selection to produce great fliers 气囊经过进化微调能造就伟大的飞行家
This unique anatomy would pave the way for 这种独特的骨骼结构为
10,000 species of birds to populate every continent on Earth 一万种鸟类繁衍于每个大陆提供可能
But 55 million years ago 但是在55万年前
one group of mammals 另一群哺乳动物
with none of the features that birds have 虽然没有鸟类的任何特征
is about to conquer the skies in a whole new way 即将以全新的方式征服天空
When the sunsets the majority of birds retreat from the sky 当太阳落山时 大多数的鸟离开天空
and gives way to an entirely different animal 另一种截然不同的动物登场
The fourth and final lineage to evolve the power of flight 第四种也是最后一种进化出飞行能力的生物
are the masters of the night 是夜空之王
Bats 蝙蝠
Bats are the only mammals 蝙蝠是哺乳动物中唯一
who have not remained ground-dwelling creatures 没有在地面生活的生物
More than just freaks of evolution 它们不止是进化上的异类
bats are one of its greatest success stories 也是进化史上最成功的例子之一
With over a thousand species worldwide 蝙蝠种类达一千种
they make up 20% of all mammals 占到所有哺乳动物的20 ％
Bats evolved the power of flight 蝙蝠飞行能力的演化
in an entirely unique way 是一个独树一帜的故事
without any of the features that make birds so successful 它没有任何鸟类成功飞行的特征
feathers hollow bones or even air sacs 中空的骨骼或羽毛甚至气囊
Birds and bats are completely separate in their evolutions 鸟类和蝙蝠是完全独立的演化
They each represent the arrival at flight by a different evolutionary pathway 它们殊途同归 共同拥有了飞行的能力
But what forces drove them to be the lone mammals in the air 但是什么力量驱使蝙蝠在约5500万年前
round fifty five million years ago? 成为空中唯一的哺乳动物 ？
And how did they manage to do something 它们如何能在夜间飞行？
very few birds ever could take to the sky at night? 这是许多鸟办不到的
We're pretty confident that 我们非常肯定
bats evolved from some kind of ancestors 蝙蝠进化而来的祖先
that with a glider that used flaps of skin 能用皮肤的薄层来滑翔
to move through the air without flapping 而不是拍打翅膀
Six groups of gliding mammals still exist 现存仍有六种具有滑翔能力的动物
from marsupials to the flying lemur and the flying squirrel 从有袋类 狐猴到鼯鼠
But only bats evolved powered flight 但只有蝙蝠进化出飞行的能力
Exactly why remains a mystery 确切原因至今仍然是一个谜
But Sharon Swartz who studies bats at Brown University 布朗大学的Sharon Swartz专门研究蝙蝠
thinks it had something to do with their ancient gliding lifestyle 认为这与蝙蝠祖先的滑翔能力有关
One major function of gliding is that it provides 滑翔的主要功能之一是它能让
an excellent way to escape predators at a moment's notice 动物在瞬间逃脱捕猎者
Physically bats acquire the power of flight 从生理上看蝙蝠获得飞行能力的方式
in a very distinct way from birds 与鸟类非常的不同
When they evolved they retain 蝙蝠在进化过程中
the five independent digits of a mammalian hand 保留了哺乳动物的五根手爪
which were covered in skin to make a wing 上面覆盖一层皮肤形成了一个翅膀
Schwartz and her colleagues Schwartz和她的同事
studied the abilities of the bat in the sky 研究蝙蝠在天空飞行的能力
by observing them flying in a wind tunnel 是通过观察其在风洞中的飞行
Bats come from animals' ancestors 蝙蝠的祖先
that have had five separate fingers 有五根单独手指
and those five separate fingers were used to control and manipulate 这五根单独的手指能够操纵和控制
lots of aspects of the environment around them 许多周围的环境因素
When bird wings evolved from dinosaur four limbs 鸟类的翅膀从恐龙的四肢进化而来时
they lost any trace of grasping digits that used to be there 失去了曾经具有抓握能力的手指
But it is these mammalian fingers that bats have retained 但是蝙蝠保留了这些哺乳动物的手指
that make bat flight so novel and so different from how birds fly 因此蝙蝠的飞行有别于鸟类
Bird wings are fixed and always in alignment 鸟的翅膀始终是对称的
mirror images of one another 互成镜像
Batd on the other hand 而另一边蝙蝠
can use their fingers in nearly twenty joints 的手指有近20多个关键
to manipulate each wing separately 能够单独操纵每边的翅膀
quickly altering the path it takes 能快速改变飞行路径
more like the oars of a boat 比起飞机的机翼
than the wings of a plane 更像是船的桨
This unique ability to control their wings 这种操控翅膀的独特的能力
has made bats the top guns of the sky 使得蝙蝠成为空中之王
They can steer and brake instantaneously 它们可以瞬间转向和制动
and are able to change their direction 改变方向的速度
up to ten times faster than a bird 最高可达鸟类的10倍
So when we look in the night sky 所以我们看向夜空
and see bats darting in a riot of angles and speeds 看到蝙蝠眼花缭乱的俯冲角度和速度
what we are seeing is not the loss of control 不是蝙蝠失去了控制
but in fact the mastering of it 实际上一切尽在掌控中
But it is when we see bats taking to the sky 但蝙蝠飞行于天空的时候
that represents something else unique 还代表了飞行能力
about their power of flight 另一独特的法宝
They are one of the few vertebrate fliers 蝙蝠是少有的几种脊椎动物
that have mastered the night sky 能够成为夜空的主人
Dr. Jim Simmons of Brown University 布朗大学的Jim Simmons教授
says a simple environmental factor may have 认为一个简单的环境因子可能
driven them there 让蝙蝠能飞起来
predation 捕猎
At night there are huge numbers of insects 在夜间有大量的昆虫
that have evolved to be active in parts of 部分为了躲避鸟类的捕食
avoiding being attacked or eaten by birds 进化出夜间活动的习惯
and the bats are out now exploiting 而如今蝙蝠找到了
this huge resource of the insect to fly at night 夜间飞虫这一巨大的食物来源
without any serious competition 并且没有任何激烈的竞争
While food may have driven some bat species into the night sky 如果食物是蝙蝠飞向夜空的原因
how do they do it? 那它们是如何做到的？
Don't forget they're flying in total darkness 不要忘记它们是在黑暗中飞行
So for the most part visual information isn't even available to them 所以大部分视觉信息是不可用的
What traits have they developed to 蝙蝠进化出了怎样的能力
allow them to navigate in the dark？ 使得它们能在黑暗中飞行？
For some bat species the answer 对于某些种类的蝙蝠
is a built-in sonar device 答案是内置声纳装置
echolocation 回声定位
Echolocation is the process 回声定位是指
where animals call out to the environment 动物对四周发出声音
and listen to the echoes of those calls 听从前方不同物体发出的回声
that return from various objects in front of it 来辨别方向的过程
In bats these calls are on a frequency too high 蝙蝠的叫声在一个很高的频率
to be heard by the human ear 人耳是不能听到的
This radar-like system gives bat an advantage 这种类雷达系统让蝙蝠在夜间飞行
when navigating at night 具有一定优势
Aside from bats only whales and dolphins 除了蝙蝠 只有鲸鱼和海豚
have evolved this system 进化出了这种系统
and bats are the only flying animal to use this technique 蝙蝠是唯一使用该技术在空中导航
to navigate their way through the skies 的飞行动物
In his lab Simmons shows just how 在实验室里Simmons向人们
precisely a bat can fly in total darkness 精确地展示蝙蝠如何在黑暗中飞行
Chains serve as obstacles 这些铁链是障碍物
and the bats shall fly in here 蝙蝠会在其中穿行
and maneuver around the chains using its sonar 利用声纳来避开这些链子
just the way it has to maneuver around the vegetation but upon 正如它避开地表的植被一样
Now the chains are black and the room is black 但是这些链子和这个房间都是黑色的
When the bats flying the lights are off 蝙蝠飞行时 灯会全关掉
as completely dark in here 因此这里完全是一片黑暗
So the bat is forced to use its sonar 所以蝙蝠必须使用声纳
instead of any residual vision that it might have 而不是任何残余的视力
Here we go 开始
No matter how many times Simmons moves the chains 不管Simmons移动多少次链条
to create new obstacles 来形成新的障碍
the result is the same 结果都是一样的
The bats safely navigate from one side of the room 蝙蝠在全黑的环境下安全地
to the other in total darkness 从房间一头飞到另一头
relying only on their echolocation 仅仅依靠它们的回声定位
These nocturnal fliers have evolved to use their ears almost 在进化中这些夜间动物的耳朵
in the same way as an eagle uses its eyes to detect prey in the air 类似在空中侦测猎物的老鹰眼睛
This highly evolved system 这种高度进化系统
is what allows bats to live and fly very successfully in total darkness 使得蝙蝠在黑暗中能够成功的繁衍和飞行
One of the things about the evolution of bats 对于蝙蝠的进化
that you can't treat their flight 它们的飞行能力
as separate from their echolocation and their hearings 和回声定位能力以及听力是密不可分的
The two go together 两者互相合作
The two works so well together 两者的搭配非常成功
that over a thousand species of bats 超过一千种蝙蝠
have radiated out across the world 遍布世界各地
Along with over 10,000 species of birds 有一万多种鸟类
and over a million species of insects 和超过一百万种的昆虫
our skies are bursting with flight both night and day 日夜盘旋于天空中
The ability to fly is arguably the evolutionary outcome 飞行能力的进化结果
that has most grabbed the human imagination 最能激发人们的想象力
And by studying the amazing features of the four different flying animals 通过研究这四种飞行生物的神奇特点
pterosaurs 翼龙
insects 昆虫
birds and bats 鸟类和蝙蝠
humankind has been able to do what they once thought 人类已经能够一偿夙愿
was impossible and take to the skies 实现不可能的飞行梦
but our man-made machines pale 但人造机器在真正
in comparison to the true marvels of natural flight 的自然飞行面前相形见绌
Due to spectacular evolutionary advancements over millions of years 由于数百万年代波澜壮阔的进化历程
land and water are no longer the only places teeming with life 陆地和水域不再是生物唯一的栖息之地