Physically, Parasaurolophus' horn is useless as a weapon.

从身体构造上来说，副栉龙的角作为武器来说毫无用途。
It's hollow and fragile, and just 2 millimeters thick.
它空心而脆弱，只有两毫米厚。
But as a communication device, it's a remarkably effective form of defense,
但是作为一个通讯设备，它是个非常有效的防御工具，
able to send out complex messages warning of danger or distress.
它可以发出警示危险或求救的复杂讯息。
Over more than 1,000 generations, this crest grows longer,
经过一千代的发展，这种冠会长得更长，
and the sounds it emits grow deeper...low frequencies able to travel long distances.
而且它发出的声音会更低，可以传播很远距离的低频率。
Highly developed communication skills become a significant evolutionary advantage.
高度发展的通讯技术变成一种进化的有利条件。
And soon enough, females only want to mate with a guy with a good set of pipes.
很快，雌性只愿意与长着一套性能优良头冠的家伙交配。
It's a sound-generating organ.
这是一个发声器官。
It can't help but generate unusual sounds by blowing air through this tube.
没什么用，但是通过吹动从管道里的空气可以产生不寻常的声音。

And because each species has its own distinct shape, each species would have its own distinct sound.
因为每个物种都有自己独特的形状，每个物种也都会有自己独特的声音。
But just how did evolution create a bony crest able to produce sounds that can travel for kilometers?
但是进化是怎样创造了一个能产生声音并传播数公里远的骨冠呢？
They simply got bigger.
其实只需要长得更大。
On the outside, the tubes appear to be only about 90 centimeters long,
从外面看，骨管似乎只有90厘米长，
but on the inside, chambers loop back and forth creating as much as 2.5 meters of resonance or nature amplification.
但是在内部管腔曲折往复形成了长达2.5米的共振腔，或者说天然放大器。
Parasaurolophus' general resonant frequency as low as 40 hertz, a sound almost as deep as a foghorn.
副栉龙的共振频率一般低达40赫兹，这种声音几乎和雾角一样低了。
We can know actually model the kind of sound that resonating chamber would make and turns out the deep sound, low frequency sound.
我们可以模拟出共振腔所发出的声音然后制造出低音，低频的声音。
Low frequency sound wave can transmit for kilometers, even through dense forest.
低频声波可以传送几公里，即使是穿过茂密的森林。
These calls warn of intruders, a significant defensive advantage.
这些叫声能通知入侵的消息是一个重要的防御优势。
And often as dinosaurs evolved over thousands of years,
伴随着恐龙上千年的进化，
their physical advantage just provided more than just one use.
这种生理优势常常有不止一个用途。
For a Parasaurolophus, the traits that make survival in a savage world possible very soon become the very same traits that attract a mate.
对于副栉龙来说，这种在野蛮世界中存活的特质可能很快成为了吸引配偶的完全相同的特质。
For a healthy male, a communication device doubles as the perfect tool for wooing the opposite sex.
对一头健康的雄性来说，通讯设备同样也是吸引异性最完美的工具。
This trombone-like structure growing out of the back of the head was used for making dinosaur music during courtship.
这个像长号一样的结构长在头的后面，是求偶期用来创造恐龙音乐的。
The males would be calling during the breeding season, attempting to influence multiple females.
雄性在求偶期将要发出叫声，试图吸引一些雌性。
And the females are calling to challenge the males to prove themselves.
雌性会回应雄性并让雄性证明它们自己。
'Cause the fundamental fact of courtship is that males lie and females are skeptical,
因为求偶期最基本的事实就是雄性爱撒谎和雌性多疑，
so the skeptical females force the male to go through more and more hoops and loops and hoops...to persuade the female to mate.
所以多疑的雌性会强迫雄性通过越来越多的考验，为了说服雌性与之交配。
It's called sexual selection.
这叫性选择。