象鸟: 重量堪比汽车的鸟界巨人(中)

Alicia wanted to investigate this. And as a paleogeneticist, she thought ancient DNA could help. The challenge was that DNA degrades fast in tropical environments.

艾丽西娅想对此进行调查。作为一名古遗传学家，她认为古代DNA(脱氧核糖核酸)可以提供帮助。而挑战在于DNA在热带环境中降解得很快。

Exactly, because you’ve got the combined effects of, you know, water damage and erosion and UV that—all of these things degrade DNA.

没错，因为这是水损害、水蚀和紫外线的综合作用，所有这些都会降解DNA。

The capacity to get genetic material, that stuff in Madagascar is really hard. I liken it to getting blood from a stone.

在马达加斯加，获得遗传物质的能力是非常困难的。我将其比作从石头里榨血，极其艰难。

But Alicia had an idea. She wondered if they could crack this big bird mystery using eggs.

但艾丽西娅有个主意。她琢磨着他们是否可以用鸟蛋来解开这个巨型鸟类的谜题。

Eggshell preserves the DNA remarkably well.

蛋壳能很好地保存DNA。

And there’s a lot of eggshell to pick from. These elephant bird eggs were huge.

有很多蛋壳可供挑选。这些象鸟蛋很大。

They were about 150 times the size of a chicken egg. And that’s larger than any dinosaur egg.

它们的大小约是鸡蛋的150倍，比任何恐龙蛋都大。

If you clutched one in your hands, it would be heavier than a bowling ball, with the shell as thick as a dinner plate.

如果你抓一个在手里，你会发现它比保龄球还重，它的壳和餐盘一样厚。

Yeah, they were about 10 kilos..., which is about 22 pounds....

是的，鸟蛋大概有10公斤重……，大约22镑重....

And unlike elephant bird bones, the eggs are easy to find.

与象鸟的骨头不同，蛋反而很容易找到。

Alicia says that if you go to the beach where she worked in the southwest of the country, you'll be walking on eggshells.

艾丽西娅表示，如果你前往她在该国西南部工作的海滩，你会在蛋壳上行走。

They’re just scattered absolutely everywhere. One person described it as paved with eggshell.

蛋壳分布在各处。有人形容那片海滩是用蛋壳铺成的。

But if collecting the eggs was over-easy, getting DNA out of them wasn’t.

如果说收集鸟蛋太容易了，那么，从中提取DNA却并不容易。

DNA can be scrambled in beach-fried eggs. So the team looked for shells buried in dig sites and dunes.

DNA可以用沙滩煎蛋炒制。因此，该团队寻找埋在挖掘场和沙丘中的蛋壳。

Then Alicia took each shell, cleaned it and ground it into a powder.

艾丽西娅捡起每个蛋壳，清洗干净，将其磨成粉末。

From that egg dust, mind-bogglingly, she pulled out pieces of DNA from birds that had been dead for 1,000 years.

令人难以置信的是，她从那些蛋壳粉末中提取出了已经灭绝1000年的鸟类的DNA片段。

It’s mind-boggling to me as well, actually.

事实上，这对我来说也难以置信。

And she used that DNA to try to figure out if those extra, extra-large elephant birds were their own species or not.

她利用这些DNA试图弄清楚那些超大型号的象鸟是否属于这个物种。

The DNA evidence from the eggshell suggests that there wasn’t two different species living in this area.

蛋壳上提取的DNA证据表明，这个地区并不存在两个不同的物种。

Basically, all of the eggshell is genetically identical.

基本上，所有蛋壳的基因都完全相同。

So if we were expecting that the largest elephant birds were a different species, then we would have seen some genetic difference in the eggshell, but we don’t see that.

如果我们料想最大的象鸟属于不同的物种，那么，我们就会在蛋壳上发现一些基因差异，但我们并没有发现不同。

So what explains the XXL bones? One possibility: big mamas.

那么如何解释超大型号的骨骼呢? 一种可能是: 大骨骼的鸟妈妈。

The very big elephant birds were females, and the slightly smaller ones were the males, we think.

我们认为，非常庞大的是雌性象鸟，稍微小一点的是雄性象鸟。

Mini-er males aren’t uncommon in birds because lady birds have to produce eggs, and that takes a lot out of them, literally.

雄鸟体型偏小在鸟类中并不罕见，因为雌鸟必须产卵，这确实会消耗掉很多。

Birds make eggshells from materials from inside their hollow bones.

雌鸟产卵以中空骨头里的物质为材料。

I mentioned that these thigh bones were 30 centimeters, a foot in circumference.

我提到过，这些大腿骨的周长是30厘米，也就是一英尺。

And one of the reasons for that is that the females would have stored materials within those in order to make the eggs.

雌鸟体型偏大的一个原因是，雌鸟会在骨头里面储存物质以便产卵。