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中国发现化石将灵长目历史提前800万年

Palm-Size Fossil Resets Primates’ Clock, Scientists Say
中国发现化石将灵长目历史提前800万年

A nearly complete skeleton of a tiny, ancient primate — one that weighed no more than an ounce, had a tail longer than its body and would fit in the palm of your hand — is the earliest well-preserved fossil primate ever found, dating back some 55 million years and dialing back the fossil record for primates by an impressive eight million years, a research team declared on Wednesday.

一个研究小组周三宣布,他们发现了一个小型古灵长目动物的骨骼化石,这副近乎完整的化石重量不超过1盎司(约合28.3克),尾巴比身体还长,你可以把它放在手掌上。这是人们迄今发现的最早的保存完好的灵长目动物化石,其历史可以追溯到大约5500万年以前,了不起地把灵长目动物的化石记录提前了800万年。

The finding adds weight to the evidence that primates originated in Asia — not Africa — and that they emerged relatively soon after the extinction of the dinosaurs, which happened about 66 million years ago.

这项发现进一步证明,灵长目动物源于亚洲,而不是非洲。它们是在恐龙灭绝(大概发生在6600万年之前)相对不久之后出现的。

The older date brings scientists closer to pinpointing a pivotal event in primate and human evolution: the divergence between the lineage leading to anthropoids — which include modern monkeys, apes and humans — and the one leading to tarsiers.

这个更古老的日期使科学家能够更准确地研究灵长目动物和人类演化史中的一个关键事件,即发展为类人猿(包括现代猿猴、猩猩和人类在内)的一支和发展为眼镜猴的一支出现分化。

In a report published in the journal Nature, an international team of paleontologists led by Xijun Ni of the Chinese Academy of Sciences in Beijing said that the skeleton, recovered from an ancient lake bed in Hubei Province in central China, set a new benchmark for the time that primates started roaming the planet.

由在北京的中科院研究员倪喜军所领导的国际古生物学家小组在发表于《自然》(Nature)杂志上的报告中说,这副骨骼是在中国中部省份湖北省一个古老湖泊的沉积岩中发现的,它更新了灵长目动物出现在地球上的时间。

The primate skeleton belongs to a species never seen before, one the researchers identified as the earliest known ancestor of tarsiers — a type of small, nocturnal primate living today in Southeast Asian forests. This unprepossessing early primate was even smaller than today’s smallest primate, the pygmy mouse lemur of Madagascar.

这副灵长目动物骨骼属于一个前所未见的物种,研究人员认为它是眼镜猴目前已知的最早的祖先。眼镜猴是一种生活在东南亚森林中的小型夜行灵长目动物。这种外表并不出众的早期灵长目动物甚至比当今最小的灵长目动物马达加斯加岛矮鼠狐猴还要小。

Dr. Ni said in a statement that the findings represent “the first time that we have a reasonably complete picture of a primate close to the divergence,” calling it “a big step forward in our efforts to chart the course of the earliest phases of primate and human evolution.”

倪喜军博士在一份声明中说,这些发现表明“我们首次对接近那个分化点的灵长目动物有了一个较为全面的了解,”他还说这个发现“在绘制灵长目动物和人类演化最初阶段的工作上迈出了一大步”。

K. Christopher Beard, a paleontologist at the Carnegie Museum of Natural History in Pittsburgh and an author of the journal report, said: “We’ve heard of the ‘out of Africa’ theory of human evolution, but that’s recent history. So there may now be the ‘into Africa’ problem.”

匹兹堡卡内基自然历史博物馆(Carnegie Museum of Natural History)的古生物学家、上述报告的作者之一K·克里斯托弗·比尔德(K. Christopher Beard)说:“我们听说过人类演化史的‘走出非洲’理论,但这只是近期的历史。所以,现在可能还有一个‘走进非洲’的问题。”

How and when did some primates finally make it to Africa, which was an island until as recently as 16 million years ago, to set in motion the emergence of the human species?

直到1600万年前,非洲都一直是一座孤岛,那么一些灵长目动物是怎样、何时来到非洲并开始向人类演化的呢?

There is evidence that 38 million years ago, some primates had apparently crossed open water to colonize the African continent.

有证据表明,3800万年前,一些灵长目动物似乎曾跨越开阔的水面,来到非洲大陆生活。

The fossil from Hubei does not answer the question of how that happened, but it does give paleontologists plenty to work on for years to come. The skeleton “differs radically from any other primate, living or fossil, known to science,” Dr. Beard said. “It looks like an odd hybrid, with the feet of a small monkey, the arms, legs and teeth of a very primitive primate and a primitive skull bearing surprisingly small eyes.”

这副来自湖北的化石并没有回答前述情况是如何发生的,但是它确实会让古生物学家在未来几年内都有事可做。这副骨骼化石“与学界所了解的其他灵长目动物——不论是现存的还是化石——都有很大差异,”比尔德说,“它看起来就像一个奇怪的杂交品种,长着小型猿猴的脚,但四肢和牙齿又像非常原始的灵长目动物,头盖骨构造简单,眼睛极小。”

Some of the skeleton’s anatomical characteristics resemble in miniature those of its tarsier lineage. Its head and trunk were less than four inches long, the tail a little more than five inches long. Some characteristics, like the monkeylike heel and ankle, appear to reaffirm the close tarsier connection to anthropoids, which is why the species has been named Archicebus achilles, a reference to the best-known heel bone in Western culture.

骨架的某些解剖学特征和眼镜猴家族相似,只是更小。它的头和身体不到四英寸(约合10厘米)长,尾巴长五英寸多一点。有一些特征,比如和猴子类似的脚踵和脚踝,似乎可以进一步证明,眼镜猴与类人猿的近亲关系,这也是为什么这个物种被命名为阿喀琉斯基猴,用了西方文化中那块著名脚踵骨的典故。

The skeleton was found by a farmer a decade ago in a rock near the course of the modern Yangtze River. But it took years of analysis to figure out how to classify the surprising-looking creature. Even today, not all researchers agree. For clues, the researchers looked to the previously oldest primate fossil specimen, a skeleton from Germany that was named in 2009 as Darwinius masillae. But the team concluded that the skeleton from Hubei, which is much smaller, belonged to an entirely separate branch of the primate family tree.

这些骨架是十年前由一位农民在长江现在的河道附近的一块岩石里发现的。但是用了好多年时间才弄明白该如何给这个长相奇特的动物归类。即便今天在研究人员中间还是存在争议的。为了寻找线索,研究人员找出了先前所知最古老的灵长目动物化石标本,2009年被命名为麦塞尔达尔文猴(Darwinius masillae)的一具在德国发现的骨架。但是研究团队得出的结论是,湖北发现这具比麦塞尔达尔文猴小很多的骨架,属于另一个完全不同的灵长目动物谱系。

Daniel L. Gebo, a member of the team from Northern Illinois University, said the foot bones “made us stop and think, what is this thing?” Finally, the researchers decided the weight of evidence favored inclusion of the skeleton on the tarsier family tree.

研究小组成员、北伊利诺伊大学的丹尼尔·L·盖博(Daniel L. Gebo)说,脚部骨骼“让我们停下来思考,这是个什么东西?”最终研究人员根据证据权重倾向于将其归入到眼镜猴这一类。

They also agreed that findings strongly supported Asia, not Africa, as the most likely continent of primate origins. No known primate fossils of such antiquity have been found in Africa, which the anthropoids eventually did colonize, evolving into Homo sapiens only about 200,000 years ago.

他们还一致认为,这些发现有力地支持了灵长目动物最有可能的发源地是亚洲而不是非洲这一观点。类人猿最终的确是在非洲生存了下来,并在大约20万年前演化为智人,不过在非洲没有发现过年代如此久远的灵长目化石。

Dr. Beard imagined that the creature, being so small and metabolically active, must have spent its days (it was not nocturnal, as its tarsier descendants are) as “a kind of frenetic animal, anxious and agile, climbing and leaping around” in the humid tropical world it inhabited. “Amazing,” he said, pausing. “A planet of the apes before there were any apes.”

按照比尔德的设想,这种动物这么小,新陈代谢又如此旺盛,白天的时候(跟它的眼镜猴后代不同,它不是夜行动物)是“某种狂躁的兽类,焦虑而机敏,攀爬纵跃个不停,”在潮湿的热带地区生活。“多精彩,”他停顿了一下,“一个还没有出现猿的‘人猿星球。’”

The world inhabited by Archicebus achilles, 55 million years ago, was very different from ours. Non-avian dinosaurs had died out, and mammals were coming into their own. The entire planet was a natural greenhouse, with life-changing tropical or subtropical rain forests growing everywhere and palm trees as far north as Alaska. Philip D. Gingerich, a paleontologist at the University of Michigan, Ann Arbor, who is an authority on primate evolution but was not involved in this research, said in an e-mail that it was “less clear to me that the Archicebus specimen” belonged in the tarsier lineage. Dr. Gingerich agreed, however, that the new skeleton was close to the divergence between the anthropoid and tarsier branches of primates. He said he expected further research to “almost certainly yield additional important information about the skull and dentition, the forelimbs and the hind limbs.”

阿喀琉斯基猴生活的那个5500万年前的世界跟我们的世界很不一样。非鸟类恐龙已经灭绝,哺乳动物正在成形。整个星球是一个自然温室,令生态环境剧变的热带或亚热带雨林遍地生长,棕榈树一直往北长到了阿拉斯加。密西根大学安娜堡分校(University of Michigan, Ann Arbor)化石学家菲利普·D·金吉尔里奇(Philip D. Gingerich)是灵长目演化方面的权威,但是没有参与本次研究,他在一封电子邮件中说,对阿喀琉斯基猴标本属于眼镜猴这一宗系的说法,“在我看来没那么确凿无疑。”不过他也认为,新发现的骨架接近灵长目类人猿和眼镜猴的分化点。他说自己推测,如果继续研究下去,“几乎肯定能够得出更多关于颅骨和齿列、前肢和后肢的重要信息。”

Another member of the group analyzing the new skeleton, John J. Flynn, curator of fossil mammals at the American Museum of Natural History in New York, said the research took 10 years to complete because “we applied rigorous testing to all our ideas and hypotheses — convincing all our own collaborators first.”

分析新发现骨架的另一位小组成员、位于纽约的美国自然历史博物馆(American Museum of Natural History)古哺乳动物策展人约翰·J·弗林(John J. Flynn)说,这项研究花费了10年才完成,因为“我们对所有的想法和假设都进行了严密的验证——首先要说服我们自己的所有合作者。”

“Some may want to take a shot at us,” Dr. Flynn said, but the analysis involved “intensive international cooperation behind the scenes at several museums.”

“可能有人会想挑战我们一下,”弗林说,但是研究分析涉及了“多家博物馆在公众视野之外的严密国际合作。”

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