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This is a song sung by a brown thrasher.
这是一段褐弯嘴嘲鸫的鸟鸣。
But that's just one of the thousand or more that it knows, and it's not the only avian virtuoso.
它会唱数以千计这样的旋律，而且它并不是唯一的鸟类歌唱家。
A wood thrush can sing two pitches at once.
棕林鸫可以同一时间唱出两种不同的音调。
A mockingbird can match the sounds around it, including car alarms.
嘲鸫则可以模仿它周围的声音，这包括车辆警报声。
And the Australian superb lyrebird has an incredible, elaborate song and dance ritual.
而澳大利亚大琴鸟有令人赞叹、极其精美的歌声和舞蹈仪式。
These are just a few of the 4,000 species of songbirds.
它们只是4千多个鸣鸟物种中的几种。
Most birds produce short, simple calls, but songbirds also have a repertoire of complex vocal patterns
大多数鸟类只能发出短促、简单的叫声，但鸣鸟则有多样化的复杂发音形式，
that help them attract mates, defend territory, and strengthen their social bonds.
帮助它们吸引配偶、捍卫领土、以及巩固它们的群居关系。
Each songbird species has its own distinct song patterns, some with characteristic regional dialects.
每一个鸣鸟物种都拥有自己独特的歌唱形式，有些则表现出了特有的地方特色。
Experienced listeners can even distinguish individual birds by their unique songs.
熟练的听者可以通过个别鸟类独特的歌声来分辨它们的种类。
So how do birds learn these songs in the first place?
那么，鸟类是如何学会这些旋律的呢？
How do they know to mimic the songs of their own species?
它们又怎么如何知道模仿自己物种的旋律呢？
Are they born knowing how to sing?
它们鸣唱的本领是与生俱来的吗？
A lot of what scientists know about bird song comes from studying zebra finches.
科学家关于鸟类鸣唱的很多知识是通过观察斑胸草雀得来的。
A baby male zebra finch typically learns to sing from its father or other males, starting while it's still a fledgling in the nest.
一只小雄性斑胸草雀通常从它父亲或其它雄性那儿学习鸣唱，这一过程从它还是巢中雏鸟时就开始了。
First comes a sensory learning phase, when the baby finch hears the songs sung around it and commits them to memory.
它首先步入的是感官认知阶段，也就是当雏草雀听到周围的旋律时会将其牢记在脑中。
The bird starts to vocalize during the motor learning phase, practicing until it can match the song it memorized.
在运动认知阶段，草雀开始把旋律唱出来，不断地练习，直到唱得跟它记忆中的一致。
As the bird learns, hearing the tutor's song over and over again is helpful -- up to a point.
草雀学习歌唱的同时，不断聆听导师重复的歌声在一定程度上对它也有帮助。
If he hears it too many times, the imitation degrades... and the source matters.
如果它听得太频繁，模仿效果就会减弱，而且旋律来源也很重要。
If the song is played through a loudspeaker, he can't pick it up as easily.
如果旋律是通过扬声器播放出来的，它就不能轻易地学会。
But hide the same loudspeaker inside a toy painted to look like a zebra finch, and his learning improves.
但是如果把扬声器藏在一个涂得像一只斑胸草雀的玩具里，它的学习能力就会大大增加。
What if the baby never hears another zebra finch's song?
要是雏鸟不曾听过其它斑胸草雀的旋律呢？
Interestingly enough, it'll sing anyway.
有趣的是，它仍然会鸣唱。
Isolated finches still produce what are called innate or isolate songs.
被孤立的草雀仍旧会唱出称为本能或孤立的旋律。
A specific tune might be taught, but the instinct to sing seems to be hardwired into a songbird's brain.
一段特定的旋律也许需要指导，但是鸣唱的本性似乎已经牢牢地嵌入鸣鸟的脑子里。
Innate songs sound different from the "cultured" songs learned from other finches -- at first.
本能旋律起初听起来跟从其它草雀那里学来的“受教育”旋律不一样。
If isolated zebra finches start a new colony, the young birds pick up the isolate song from their parents.
如果被孤立的斑胸草雀开始成立一个新的群体，雏鸟就会从它们的父母那里学会孤立的旋律。
But the song changes from generation to generation.
但是同样的旋律会一代接一代地改变。
And after a few iterations, the melody actually starts to resemble the cultured songs sung by zebra finches in the wild.
经过几代后，它们的旋律其实就会开始跟野外的斑胸草雀所唱的“受教育”旋律相似。
Something about the learning process must be hardwired, too,
学习过程中的某个元素肯定也牢牢地嵌入了鸟内的大脑中，
drawing the birds towards the same song patterns again and again.
不断地把它们牵引到同样的旋律形式。
This means that basic information about the zebra finch song must be stored somewhere in its genome,
这表明，有关斑胸草雀鸣唱旋律的基本信息肯定是储存在它的基因组内某个地方，
imprinted there by millions of years of evolution.
是经历了上百万年的演化后遗留下来的。
At first, this might seem odd, as we usually think of genetic code as a source of biochemical or physical traits,
这乍看起来很不寻常，因为通常我们认为，基因决定的是生化或生理特征，
not something like a behavior or action.
而并非行为或行动。
But the two aren't fundamentally different; we can connect genomes to behavior through brain circuitry.
但其实，这两种特征本质上区别不大；我们可以通过脑神经环路把基因组和行为联系起来。
The connection is noisy and quite complex.
这种联系很错综复杂。
It doesn't simply map single genes to single behaviors, but it exists.
它不单单只把一种基因跟一种行为联系起来，但是这种联系确实存在。
Genomes contain codes for proteins that guide brain development,
基因组含有协助脑部发育所需蛋白质的遗传密码，
such as molecules that guide the pathways of developing axons, shaping distinct circuits.
例如引导轴突生长途径的分子，能够塑造独特的神经环路。
Birds' brains have so-called "song circuits" that are active when the birds sing.
鸟类的脑袋有所谓的“旋律环路”，在鸟类鸣唱时会被激活。
These circuits also respond to the song of a bird's own species more strongly than to other species' songs.
这些环路在鸟类听到同类鸣唱时所产生的反应，会比听到非同类鸣唱的反应更强烈。
So the theory is that a bird's genes guide development of brain circuits that relate to singing and the ability to learn songs.
理论推测，和鸟类鸣唱以及学习旋律的能力有关的脑环路的发展是由基因引导的。
Then, exposure to songs shapes those neural circuits to produce the songs that are typical to that species.
鸟类接触旋律后将会塑造那些神经环路，使它们能鸣唱出同类特有的旋律。
Genetically encoded or innate behaviors aren't unique to songbirds. They're widespread in the animal kingdom.
由基因决定或天生的行为并非鸣鸟独有。这种现象在动物界中随处可见。
Spectacular examples include the long-distance migrations of monarch butterflies and salmon.
典型的例子包括帝王蝶和鲑鱼的长途迁徙。
So what does this mean for humans?
那么，这对人类来说有什么意义呢？
Are we also born with innate information written into our genomes that helps shape our neural circuits,
我们是否也生来就拥有帮助塑造我们神经环路的基因组信息，
and ultimately results in something we know?
并且最终产生了我们所知道的一切？
Could there be some knowledge that is unique and intrinsic to humans as a species?
有没有什么知识是我们身为人类独有以及固有的呢？
