Narrator: Listen to part of a lecture in a paleontology class.

旁白：听一段古生物学的演讲。

Professor: As we’ve discussed, birds are apparently descendants of dinosaurs and share many commonalities with some dinosaur species, like…um…feathers and maybe even flight and of course egg laying.

教授：就像我们讨论过的那样，鸟类很明显是恐龙的后裔，并且和一些恐龙种类有着很多共性，如羽毛啊，也许甚至是飞行啊，当然也包括下蛋。

OK. So, many paleontologists, myself included, have wondered about other similarities between dinosaurs and birds.

所以，很多古生物学家，也包括我自己在内，有思考过恐龙和鸟类之间其他的相似性。

Since adult dinosaur fossils have sometimes been discovered near or on top of nests, we’ve been looking into dinosaur parenting behavior.

因为有的时候可以在鸟巢附近或者顶部发现一些成年恐龙的化石，我们就得以探究以下恐龙的教养行为。

Student: Parenting behavior, well, that sounds so gentle and caring.

学生：教养行为，好吧，那个听上去很温和、很关怀。

But dinosaurs were ferocious reptiles and reptiles don’t take care of their young, do they?

但是恐龙是残忍的爬行类动物，爬行类动物是不照顾他们的幼崽的，不是吗？

Professor: Well, some reptiles incubate their eggs, crocodiles do.

教授：好的，有一些爬行动物是孵蛋的，鳄鱼就会。

And as for popular attitudes towards dinosaurs…well, take the Oviraptor for instance.

针对恐龙比较普遍的看法是……好的，我们拿窃蛋龙作例子。

In the 1920s, a paleontologist discovered the fossil remains of a small dinosaur near a nest containing eggs.

在20世纪20年代，一个古生物学家在一个有蛋的鸟巢附近发现了一个小恐龙的化石。

He assumed the dinosaur was stealing the eggs, so he named it Oviraptor that means egg thief in Latin, which fueled the generally negative public image of such dinosaurs.

他假定那个恐龙是在偷蛋，因此他命名它为窃蛋龙，在拉丁语里的意思就是偷蛋的窃贼，这个促使了大众对于这种恐龙的负面印象。

But by the 1990s, other experts had convincingly made the case that instead of robbing the nest; the Oviraptor was probably taking care of the eggs.

但是，直到20世纪90年代，其他一些专家很肯定地给出理由，指出窃蛋龙很可能是在照顾这些蛋，而不是偷蛋。

You see, dinosaurs’ closest living relatives – birds and crocodiles – display nesting behavior.

你是知道的，恐龙最近的近亲——鸟类和鳄鱼——都表现出了孵蛋的行为。

And dinosaur fossils have been found in postures that we now believe to indicate brooding behavior--that is, sitting on the eggs until they hatch.

并且，恐龙化石中所呈现出坐在蛋上孵蛋的姿态，我们现在认为这个就预示着一种孵蛋的行为。

So we are curious about the type of care dinosaurs gave to their young.

所以，我们对于恐龙给予他们幼崽怎样的呵护感到好奇。

And we’d like to figure out which dinosaur parent, the male or the female gave the care.

并且，我们想要断定到底是恐龙父母中的哪一方，雄性还是雌性，来照顾蛋。

Student: Shouldn’t the behavior of crocodiles and birds give us some clues then?

学生：那么是不是鸟类和鳄鱼的行为会给我们一点启示呢？

Professor: Well, with crocodiles, it is the female who guards the nest, and with birds, it depends on the species, it can be the male or the female that takes care the eggs, or both.

教授：好的，对于鳄鱼来说，是由雌性来护着巢穴的；而对于鸟类，这个取决于它们的品种，可能是雄性，也可能是雌性，或者两者一起照顾蛋。

In over 90 percent of all bird species, both parents take care of the eggs and the young birds.

超过90%的鸟类中，父母双方都照顾蛋和幼鸟。

Student: But sometimes it’s just the male?

学生：但是有些时候只有雄性？

Professor: Well, exclusive care by the male parent is much less common, but it does occur.

教授：仅由雄性来照顾是不太常见的，但是这个确实存在。

Now, for animals other than birds, the care of young by both parents is pretty unusual in the animal kingdom.

现在，对于鸟类以外的一些动物，在动物这个王国中很少有父母双方共同哺育幼崽的。

Males contribute to parental care in fewer than five percent of all mammalian species.

在哺乳类的动物中，由雄性参与到哺育中的情况少于5%。

It’s even less frequent among reptiles.

在爬行动物中就更少了。

And exclusive care by the male is very rare.

并且，由雄性单独哺育的情况几乎是很罕见的。

So researchers have wondered about the evolution of male parenting behavior in birds for quite some time.

所以，研究人员很长一段时间都对鸟类的教养行为感到困惑。

And now there’s research showing that for some of the birds’ dinosaur relatives, it’s likely that the male parent was also in charge of taking care of the eggs.

现在，有研究显示，在一些鸟类恐龙的近亲中，雄性负责照顾蛋是很有可能的。

Student: How did they figure that out?

学生：他们是怎么发现的？

Professor: Well, first they looked at clutch volume, that’s the number of eggs in the nest of crocodiles, birds and three types of dinosaurs, including Oviraptors that are thought to be closely related to the dinosaur ancestors of birds.

教授：首先，他们会着眼于窝卵数，也就是在鳄鱼、鸟类及三种恐龙巢穴中蛋的数量，其中也包括被认为和古代鸟类紧密相关的窃蛋龙。

So when researchers examined fossilized remains of nests, they found that the dinosaurs had larger clutch volumes, more eggs in the nests that is, than most of the crocodiles and birds that were studied.

当研究人员检查巢穴的化石时，他们发现恐龙有着较大的窝卵数，比大部分被研究的鳄鱼和鸟类巢穴中的蛋都要多。

But, and this is important, their clutch volumes matched those of birds that have only male parental care.

但是这个很重要，他们的窝卵数和只由雄性来进行教养行为的鸟类吻合。

You see, bird species in which only the males take care of the nest tend to have the largest clutches of eggs.

只由雄性来照看鸟巢的鸟类往往有着最大的窝卵数。

Student: So what’s the connection between bird and dinosaur behavior?

学生：所以鸟类和恐龙之前的行为有什么联系？

Professor: Well, researchers now believe, because of this study, that the male parenting behavior of these birds might have its origins in the behavior of dinosaurs.

教授：由于这个研究，研究人员现在认为，这些鸟类的教养行为可能是起源于恐龙。

Student: Based only on evidence of clutch volume size, the number of eggs?

学生：仅仅基于由于窝卵数、蛋的数量，这个证据？

Professor: No, there’s more.

教授：不，还有其他的。

They also examined the fossilized bones of those three types of dinosaurs that were found on or near nests to determine their sex.

他们还检查了在巢穴附近发现的，这三种恐龙的骨骼化石，来决定他们的性别。

You see, adult female birds during egg production produce a layer of spongy bone tissue inside certain long bones.

你是知道的，成年雌鸟在产蛋中会形成特定的长骨中为形成一层松质骨组织。

And so did female dinosaurs of the kinds that were investigated.

所以这种雌性恐龙就被研究了。

This spongy tissue serves as a source of calcium for eggshell formation.

这种松质组织充当了蛋壳形成的钙质的来源。

But when the dinosaur fossils were examined, there were no spongy bone deposits.

但是，当恐龙化石被检查的时候，那里并没有松质骨的沉积物。

Student: Meaning that those dinosaurs on the nests were probably adult males who wouldn’t have needed calcium for making eggshells.

学生：这就表示在鸟巢中的恐龙可能是成年雄性恐龙，它们并不需要钙质去形成蛋壳。

Professor: Exactly. And then there’s this: birds like the kiwi, the ostrich and the emu; they share certain physical characteristics with these dinosaurs.

教授：正确。然后就有了这个：像是几维、鸵鸟、鸸鹋这样的鸟类，它们和这些恐龙有着特定的相同的身体特征。

And interestingly, they also show a consistent pattern of nest care by the male.

有意思的是，它们也展现出了持续由雄性照顾鸟巢的模式。