经济学人下载:无罪(2)

Working with a team of colleagues, the researchers obtained DNA from 12 woolly-rhinoceros bones collected from permafrost in Siberia,
研究人员和同事们从西伯利亚多年冻土中采集到的12根披毛犀骨头中提取到了DNA，

dating from the beginning of the Late Pleistocene, about 130,000 years ago, until the animals were on the verge of extinction.
年代区间约从13万年前的晚更新世开始，到这些动物濒临灭绝为止。

Extra DNA was recovered from one sample of rhino hair and one piece of tissue found in the stomach of a frozen wolf that had been preserved by the cold.
另外的DNA来自于一根犀牛毛发样本，以及在一只冻狼胃部发现的一块组织，这只狼被低温保存了下来。

Analysing the genetic diversity of the samples allowed the researchers to make a rough calculation of the size of the woolly-rhino population over time.
分析这些样本的基因多样性能够让研究人员粗滤估算各时期披毛犀的数量。

Rather than declining as humans arrived, the population remained stable from 29,000 years ago until 18,500 years ago,
随着人类的到来，它们的数量没有减少，而是从2.9万年前开始就保持稳定，直到1.85万年前，

just a few thousand years before the species went extinct.
此时距离该物种灭绝仅几千年。

That suggests that, far from being hunted to extinction, the rhinos co-existed stably with humans for around 10,000 years.
这表明，这种犀牛并不是被猎杀致灭绝的，约一万多年以来，它们一直都和人类稳定地共存。

Perhaps the people who encountered the beasts found them unpalatable.
大概遇到这种野兽的人发现它们超级难吃。

Or perhaps the rhinos were simply too dangerous to hunt with their simple weapons.
又或者只是因为这种犀牛太过危险，人类简单的武器无法捕获它们。

(They were the size of the modern white rhino, which is not an animal that takes kindly to being stabbed with spears.)
（它们的体型和现代白犀牛的差不多，而白犀牛可不是那种喜欢被矛穿刺的动物。）

The researchers' case is not quite conclusive.
研究人员的结论还不是很明确。

It is possible that some sort of technological advance eventually gave ancient humans the ability to hunt rhinos safely,
或许某种继续进步最终赋予了古代人类安全捕获犀牛的能力，

and that extinction followed after that breakthrough.
并且在这次突破之后，它们就灭绝了。

On the other hand, the animals' decline lines up suggestively with a rapid bout of global warming that began around 14,700 years ago.
另一方面，动物数量的减少与始于大约1.47万年前的全球变暖的迅速爆发有明显的联系。

The researchers argue that this was the more likely cause of the animal's disappearance. This time, it seems, it was Mother Nature whodunnit.
研究人员表示，这更有可能是这种动物消失的原因。这一次，似乎是大自然母亲下的手。