小小樹(shù)上古住民——科學(xué)家發(fā)現(xiàn)地球上最早的靈長(zhǎng)類

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[恐龍] died out. But Archicebus had some primitive[原始的] features[特征] we associate[把……聯(lián)系起來(lái)] with monkeys and the rest of the primates[靈長(zhǎng)類動(dòng)物]. It had big eye sockets[眼窩]， for example， and they are angled in a way that meant the animal had good stereo vision[立體視覺(jué)]. It had nails instead of claws and grasping[抓，緊握] 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[捕獲] insects. Christopher Beard： Its a fossil[化石] that shows a combination[結(jié)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（現(xiàn)代人的學(xué)名）].

Beard says the lineage[血統(tǒng)] 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[顯然地]， 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[人類學(xué)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[血緣關(guān)系] to the first primate and it could help answer some crucial[至關(guān)緊要的] 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.

這（種化石）被稱為“阿喀琉斯基猴”——大概的意思是始祖長(zhǎng)尾猴。實(shí)際上，這種生物生活在5500萬(wàn)年前，在恐龍滅絕的一千萬(wàn)年后出現(xiàn)，遠(yuǎn)比我們今天所知的猴子（生活的年代）要早。不過(guò)，阿喀琉斯基猴具備了一些靈長(zhǎng)類特征，我們可以將其與猴子以及其他靈長(zhǎng)類聯(lián)系在一起。比如它那大大的眼窩，其凹陷角度說(shuō)明這種動(dòng)物具有良好的立體視覺(jué)。它有指甲（而不是爪子）以及有抓力的足趾，還有其他獨(dú)特的特征。

這些特征大多是為了適應(yīng)樹(shù)上的生活，也許還有助于阿喀琉斯基猴捕捉昆蟲(chóng)。

克里斯托弗·比爾德：這塊化石上呈現(xiàn)出來(lái)的各種特征……是我們之前從未在任何現(xiàn)存的靈長(zhǎng)類或者類人猿化石上看到的。

克里斯托弗·比爾德在研究組工作，他來(lái)自（美國(guó)）匹茲堡的卡耐基自然歷史博物館。

該化石的發(fā)現(xiàn)者是一位中國(guó)農(nóng)民。活著的阿喀琉斯基猴只有一盎司（約28克）重，體型僅為人類的巴掌大小。雖然經(jīng)過(guò)了漫長(zhǎng)的年月，化石的骸骨依然保持完好，實(shí)在是一件了不起的事情。對(duì)進(jìn)化史來(lái)說(shuō)，這是一個(gè)特殊的時(shí)刻。第一批靈長(zhǎng)類出現(xiàn)了。隨著時(shí)間的推移，它們會(huì)不斷演化，產(chǎn)生分支，出現(xiàn)各種各樣的體型以及不同的行為特征，有的變成了猿猴，有的變成了狐猴，而其中一支最終演變成今天的我們——智人。

比爾德說(shuō)，阿喀琉斯基猴和我們也許并不是真正的同源血親。

比爾德：不過(guò)，不管怎么說(shuō)，（該發(fā)現(xiàn)的）實(shí)際成果就是——這兒有一塊化石，它非常非常接近我們的進(jìn)化分支。

而這分支看起來(lái)源自亞洲?？茖W(xué)家們?cè)凇蹲匀弧冯s志上發(fā)表文章，認(rèn)為阿喀琉斯基猴也許是目前發(fā)掘出的最古老靈長(zhǎng)類骸骨。（美國(guó)）杜克大學(xué)的人類學(xué)家理查德·凱說(shuō)，這也是可能的。這個(gè)研究領(lǐng)域并不明晰——其他的靈長(zhǎng)類化石或許也能算數(shù)。但阿喀琉斯基猴無(wú)疑是第一只靈長(zhǎng)類的近親，能夠幫助我們解答幾個(gè)關(guān)鍵的疑問(wèn)。

理查德·凱：為什么這個(gè)族群的視覺(jué)發(fā)育得如此完善？為什么它們舍棄了靈巧的爪子，手指腳趾上卻逐漸長(zhǎng)出了指甲？還有很多其他特征，我們都需要找出演變發(fā)生的原因所在。