谁杀死了猛犸象？(Who Killed the Elephants?)（在线收听）

    Hungry prehistoric hunters, not climate change, drove elephants and wooly mammoths to extinction during the Pleistocene era, new research suggests.

    在约一万年前的更新世，大象和猛犸象从地球上许多地区大量消失。一项新研究表明，导致这场灭绝的并不是气候剧变，而是饥饿的史前猎人。

    At least 12 kinds of elephants and mammoths used to roam the African, Eurasian, and American continents. Today, only two species of elephants are left in South Asia and sub-Saharan Africa. One theory for this dramatic demise holds that rapid climate shifts at the end of the most recent major ice age, some 10,000 years ago, altered vegetation and broke up habitats, causing the death of those unable to adapt to the new conditions. Another hypothesis blames prehistoric humans, whose improved weapons and hunting techniques allowed them to wipe out whole herds of elephants and mammoths (Science, 8 June 2001, p. 1888).

　　历史上曾经至少有12种大象和猛犸象漫游在非洲、美洲和欧亚大陆，但现在只剩下亚洲象和非洲象两种。有的科学家认为，在约一万年前的最近一次冰期，地球气候急剧变化，影响植被、破坏栖息地，大部分大象和猛犸象难以适应新的环境，以至灭绝。另一种假设则提出，当时的史前人类掌握了更精良的武器和更娴熟的捕猎技巧，可以猎杀整群的大象和猛犸象，致使其灭绝。

    To help resolve the debate, archaeologist Todd Surovell of the University of Wyoming, Laramie, and colleagues tested two assumptions. If humans caused the elephant and mammoth extinctions, Surovell reasoned, the timing of the die-offs in specific regions should match human expansion into those regions. On the contrary, if the extinction of these mammals were due to climate change, elephants and mammoths should remain in regions already colonized by humans and would only begin to die off once climate change occurred.

　　为了解决这个争议，美国怀俄明大学的考古学家Todd Surovell及其同事对以上两种假说进行了检验。Surovell提出，如果主要原因在于人类，那么特定地区大象和猛犸象的灭绝情况应与人类在该地区的扩张一致。相反，如果是气候导致了灭绝，那么在已经有人居住的地区，大象和猛犸象也仍然存在，直到气候变化来临。

    The team tested both theories by analyzing where and when elephants and mammoths were killed. In all, the study included 41 archaeological sites on five continents. The researchers found that, as humans migrated out of Africa, they left a trail of dead elephants and mammoths in their wake. The creatures disappear from the fossil record of a region once it became colonized by humans. Modern elephants survived in refuges uninviting to humans, such as tropical forests, says Surovell, whose team reports its findings online this week in the Proceedings of the National Academy of Sciences.

　　为此，研究小组分析了大象和猛犸象被人类捕杀的时间和地点等情况。他们对5大洲41处考古地点进行研究，结果发现，人类走出非洲的途中，身后一路留下大象和猛犸象的遗骸。某一地区一旦有人类居住，这里的大象和猛犸象就开始从化石记录里消失。Surovell提出，现代大象的祖先是因为居住在热带雨林等人类难以到达的地方，才得以存留。有关论文发表在本周的美国《国家科学院学报》(PNAS)上。

    Biologist R. Dale Guthrie of the University of Alaska in Fairbanks largely agrees with the findings, but he says more work is needed to explain why some mammoths seem to have survived in regions colonized by humans and why many modern elephants live in areas easily accessible to humans, such as the African savannah.

　　阿拉斯加大学的生物学家R. Dale Guthrie大体上同意这种看法，但认为还需要更多研究来解释一些现象，如猛犸象为何能在有人居住的地方生存，现代大象为何能生活在人类容易到达的非洲大草原等地区。