小小树上古住民——科学家发现地球上最早的灵长类

by Christopher Joyce

Its called Archicebus， roughly meaning beginning long-tailed monkey. Actually， this creature lived before the monkeys we know of today—55 million years ago， a mere ten million years after the dinosaurs[恐龙] died out. But Archicebus had some primitive[原始的] features[特征] we associate[把……联系起来] with monkeys and the rest of the primates[灵长类动物]. It had big eye sockets[眼窝]， for example， and they are angled in a way that meant the animal had good stereo vision[立体视觉]. It had nails instead of claws and grasping[抓，紧握] digits[手指或足趾]， and other unique traits[特性].

Many of these would have been good for living in trees and， perhaps， capturing[捕获] insects. Christopher Beard： Its a fossil[化石] that shows a combination[结合] of features that weve simply never seen before…in any living or fossil primate.

Christopher Beard is with the Carnegie Museum of Natural History， in Pittsburgh， and worked on the team.

The fossil was discovered by a farmer in China. Alive， the animal weighed an ounce and would fit in the palm of your hand. The skeletons[骨架] completeness[完整性] and its great age are extraordinary. It was a special time in evolution. The first primates were emerging. Over time， they would evolve and diverge[分叉] into numerous body types and behaviors； some becoming monkeys， some lemurs[狐猴]， and one would eventually evolve into us—Homo sapiens[智人（现代人的学名）].

Beard says the lineage[血统] Archicebus was on may not have been the one we came from. Beard： But in any case， the take-home picture should be that here is a fossil thats very， very close to that evolutionary divergence[分歧].

And apparently[显然地]， that divergence happened in Asia. Writing in the journal[定期刊物] Nature， the scientists say Archicebus may be the earliest primate skeleton ever found. Duke University anthropologist[人类学家] Richard Kay says， well， maybe. Its a murky[不清楚的] field of study—some other primate fossils might qualify. But Archicebus was certainly close kin[血缘关系] to the first primate and it could help answer some crucial[至关紧要的] questions.

Richard Kay： Why did this group of animals get really well-developed vision？ Why did they get rid of perfectly good claws and start to have nails on their fingers？ And a lot of other characteristics[特征]， they beg an answer as to why did this change occur.

这（种化石）被称为“阿喀琉斯基猴”——大概的意思是始祖长尾猴。实际上，这种生物生活在5500万年前，在恐龙灭绝的一千万年后出现，远比我们今天所知的猴子（生活的年代）要早。不过，阿喀琉斯基猴具备了一些灵长类特征，我们可以将其与猴子以及其他灵长类联系在一起。比如它那大大的眼窝，其凹陷角度说明这种动物具有良好的立体视觉。它有指甲（而不是爪子）以及有抓力的足趾，还有其他独特的特征。

这些特征大多是为了适应树上的生活，也许还有助于阿喀琉斯基猴捕捉昆虫。

克里斯托弗·比尔德：这块化石上呈现出来的各种特征……是我们之前从未在任何现存的灵长类或者类人猿化石上看到的。

克里斯托弗·比尔德在研究组工作，他来自（美国）匹兹堡的卡耐基自然历史博物馆。

该化石的发现者是一位中国农民。活着的阿喀琉斯基猴只有一盎司（约28克）重，体型仅为人类的巴掌大小。虽然经过了漫长的年月，化石的骸骨依然保持完好，实在是一件了不起的事情。对进化史来说，这是一个特殊的时刻。第一批灵长类出现了。随着时间的推移，它们会不断演化，产生分支，出现各种各样的体型以及不同的行为特征，有的变成了猿猴，有的变成了狐猴，而其中一支最终演变成今天的我们——智人。

比尔德说，阿喀琉斯基猴和我们也许并不是真正的同源血亲。

比尔德：不过，不管怎么说，（该发现的）实际成果就是——这儿有一块化石，它非常非常接近我们的进化分支。

而这分支看起来源自亚洲。科学家们在《自然》杂志上发表文章，认为阿喀琉斯基猴也许是目前发掘出的最古老灵长类骸骨。（美国）杜克大学的人类学家理查德·凯说，这也是可能的。这个研究领域并不明晰——其他的灵长类化石或许也能算数。但阿喀琉斯基猴无疑是第一只灵长类的近亲，能够帮助我们解答几个关键的疑问。

理查德·凯：为什么这个族群的视觉发育得如此完善？为什么它们舍弃了灵巧的爪子，手指脚趾上却逐渐长出了指甲？还有很多其他特征，我们都需要找出演变发生的原因所在。