考古新發現,人類的祖先是老鼠

As ancestors go, it might not look particularly distinguished, but this toothy rat-like creature is the forefather of us all. Remains of the little nocturnal mammal, which lived 145 million years ago, were recently discovered on the Jurassic Coast of Dorset, by paleontologists from the University of Portsmouth.

考古發現，上圖這種長相和老鼠類似的齧齒動物是人類的祖先，雖然這位祖先的外貌不是很出衆。近日，朴茨茅斯大學的古生物學者們在多賽特郡的侏羅紀海岸發現了這種生活在1.45億年前的小型夜行哺乳動物的殘骸。

The animal is the earliest in a line that would eventually lead to humans, as well as branching off along the way to evolve into creatures as diverse as Blue Whales and Pigmy Shrews.

這種遠古動物最終會進化爲人類，而且在演變過程中，還會進化成藍鯨和鼩鼱等多種不同生物。

The new species has been named ‘Durlstotherim newmani’, after keen amateur paleontologist Charlie Newman, 51, the landlord of the Square and Compass in Worth Matravers who founded his own fossil museum in the pub, and helped scientists collect the new specimens.

新發現的這個物種被命名爲Durlstotherim newmani，得名於熱心的業餘古生物學家查理?紐曼的名字。51歲的紐曼是沃斯麥特勒佛的Square and Compass酒館的老闆，他在酒館裏創辦了自己的化石博物館，幫助科學家收集到了這些新樣本。

Mr Newman, made headlines in 2015 when he built his own 12ft high ‘Stonehenge’ using 35 tonnes of timber in a field he owns in the village, although he was later ordered to tear it down by Purbeck District Council.

紐曼曾在2015年用自己農場裏的35噸木材建造了一個12英尺高的“巨石陣”，並因此登上了新聞頭條，不過後來波倍克區議會命他將其拆除。

The new species were identified from just a handful of fossilised teeth which were found by Portsmouth University undergraduate Grant Smith earlier this year, and identified by Dr Steve Sweetman, a research fellow at the university.

今年早些時候，朴茨茅斯大學的本科生格蘭特?史密斯發現了一把牙齒化石，該校的研究員史蒂夫?斯威特曼博士根據這些化石識別出了這一新物種。

Dr Sweetman said: “Grant was sifting through small samples of earliest Cretaceous rocks collected on the coast of Dorset as part of his undergraduate dissertation project in the hope of finding some interesting remains.

斯威特曼博士說：“格蘭特當時正在篩選從多賽特海岸上收集到的最早的白堊紀小塊岩石樣本，希望能找到一些有趣的遺骸用於他的本科論文項目。”

“Quite unexpectedly he found not one but two quite remarkable teeth of a type never before seen from rocks of this age. I was asked to look at them and give an opinion and even at first glance my jaw dropped.

“出乎意料的是，他找到了不止一塊，而是兩塊非常特別的牙齒，這種牙齒類型從未在這個年代的岩石中見過。他請我過去看一下，想聽聽我的意見，結果我纔看了一眼就驚呆了。”

“The teeth are of a type so highly evolved that I realised straight away I was looking at remains of Early Cretaceous mammals that more closely resembled those that lived during the latest Cretaceous - some 60 million years later in geological history.

“這種牙齒的進化程度很高，我馬上就意識到這可能是白堊紀早期哺乳動物的遺骸，白堊紀早期哺乳動物和6000萬年後的白堊紀末期哺乳動物更相似。”

“The specimen is named after a pub landlord because he is a keen amateur paleontologist and has a small museum in his pub. He helped us collect samples and was otherwise very helpful and hospitable.”

“這個標本得名於一個酒館老闆，因爲他是個熱心的業餘古生物學家，在他的酒館有個小型博物館。他幫我們收集樣本，在其他方面也非常樂於助人、熱情好客。”

Dr Sweetman believes the mammal was a small, furry creature and most likely nocturnal. A second species was also identified and named after scientist, Paul Ensom. The creatures probably lived in burrows feeding on insects, or plants.

斯威特曼博士認爲這種哺乳動物是一種毛絨絨的小動物，極有可能在夜間活動。第二個標本也已經確認並以科學家保羅?恩索姆的名字命名。這些動物很可能居住在地洞中，以昆蟲或植物爲食。

“The teeth are of a highly advanced type that can pierce, cut and crush food,” added Dr Sweetman.

斯威特曼博士補充說：“這些牙齒是高度進化的，可以刺穿、咬斷和碾碎食物。”

“They are also very worn which suggests the animals to which they belonged lived to a good age for their species. No mean feat when you’re sharing your habitat with predatory dinosaurs.”

“這些牙齒磨損很嚴重，這意味着牙齒主人在它的種羣中很長壽。要知道，和食肉恐龍共存絕非易事。”

The teeth were recovered from rocks exposed in cliffs near Swanage which has given up thousands of iconic fossils.

這些牙齒是在斯沃尼奇附近的懸崖上的岩石中找到的。在斯沃尼奇一帶曾發現數千塊重要化石。

Dave Martill, Professor of Palaeobiology, at Portsmouth was originally shown the teeth by Mr Smith, and confirmed they were mammalian, but was puzzled as to what they were doing in such an old layer of rock.

朴茨茅斯大學的古生物學教授戴維?馬提爾最開始是從史密斯那裏看到這些牙齒的，他確定這些牙齒是哺乳動物的，但是對於這些牙齒爲什麼會出現在古老的岩層中很迷惑。

Mammal teeth evolved over time, from very simple ones that were not very efficient, to molar-like ridged teeth which could tear, chew and grind food very easily. Teeth as well-evolved as Durlstotherim newmani, have previously only been found in rock layers from, the late Cretaceous, between 86 and 66 million years ago.

隨着時間的流逝，哺乳動物的牙齒從非常簡單的效率不高的牙齒進化成可以輕易地撕裂、咀嚼和碾碎食物的接近臼齒的脊狀牙齒。像Durlstotherim newmani一樣高度進化的牙齒，先前只在8600萬到6600萬年前的白堊紀晚期的岩層中找到過。

Professor Martill said: “We looked at them with a microscope but despite over 30 years’ experience these teeth looked very different. Steve made the connection immediately.

馬提爾博士說：“我們用顯微鏡觀察了這些牙齒，儘管擁有三十多年的從業經驗，這些牙齒在我看來仍然非常異樣。但史蒂夫馬上就想到了。”

“The Jurassic Coast is always unveiling fresh secrets and I’d like to think that similar discoveries will continue to be made right on our doorstep.”

“侏羅紀海岸總是不斷地揭開新的祕密，我期待類似的發現會繼續在我們眼前涌現。”

Dr Sweetman said the finds rewrite the history of mammal evolution.

斯威特曼博士說，這一發現改寫了哺乳動物的進化史。

“In the world of palaeontology there has been a lot of debate around a specimen found in China, which is approximately 160 million years old,” he added.

他說：“在古生物學領域中，學者們對於在中國發現的一個大約有1.6億年曆史的標本有很多爭論。”

“This was originally said to be of the same type as ours but recent studies have ruled this out. That being the case, our 145 million year old teeth are undoubtedly the earliest yet known from the line of mammals that lead to our own species.”

“最初人們認爲該標本和我們發現的標本是同一種，但是最近的研究排除了這種可能性。既然如此，我們所發現的1.45億年曆史的牙齒主人無疑是已知最早的人類的哺乳動物祖先。”