经济学人下载:熊猫遗传学:熊猫的远亲是谁?(2)

And most curiously of all, both have a sixth digit on their forepaws—a kind of ancillarythumb derived from one of the bones of the wrist that helps them hold bamboo stalks for consumption.
最令人惊奇的是，它们的前爪上都长有第六指，是从腕骨长出用来帮助它们在进食时拿住竹茎的辅助拇指。

These common features led Hu Yibo of the Institute of Zoology, in Beijing, and his colleagues, to wonder if the two vegetarian carnivores also shared genetic modifications that might explain those features.
基于这些共同特征，北京动物研究所的胡一波和他的同事们设想，这两种食肉目食草动物是否共有一种能解释这些特征的修饰基因。

And, as Dr Hu observes in a paper just published in the Proceedings of the National Academy of Sciences, they do.
正如胡博士刚刚在《美国国家科学院院报》发表的论文中所说的，它们确实共有。

To search for such genetic commonalities, Dr Hu and his colleagues compared the DNA of the two pandas with that of four other members of the Carnivora:
为了找到这样的遗传共性，胡博士团队将两只熊猫的DNA与另外4种食肉目动物

polar bears (close relatives of giant pandas), ferrets(close relatives of red pandas), and tigers and dogs (close relatives of neither).
（北极熊（大熊猫的近亲），白鼬（小熊猫的近亲），老虎和狗（非两者近亲））的DNA进行比较。

If pandas share features of their DNA with each other, but not with the four comparison species, he reasoned,
如果熊猫们有相同的DNA特征，而四种对照物种没有熊猫所共有的DNA特征，

then it is likely that those features encode recent adaptations common to the two of them.
他则推理很有可能这些DNA特征编码了它们两者间近代的共同特性。

Altogether, the team identified 70 genes (out of the 20,000 or so that mammals have) which sport bits of DNA that seemed to be shared.
研究小组从哺乳动物约20000个基因中，确定了可以共有的70个DNA片段。

They also found ten genes which have been disabled by crippling mutations in both of the pandas, but not in the other four species.
他们也在两种熊猫中找到了十个因严重突变而丧失功能的基因，而其他四个物种中并未发现。

Not all of the shared genetic features obviously tied in with the shared peculiaritiesof pandas, but some did.
尽管哺乳动物共有遗传特征并不都与熊猫的特性一致，但有些确实具有一定的关系。

These fell into three categories: genes affecting anatomy, genes affecting appetite and genes affecting the digestion and metabolism of nutrients.
这分为三类：影响动物体结构的基因，影响食欲的基因和影响营养物质消化和新陈代谢的基因。