Two new species of prehistoric primate were recently identified by scientists studying fossils from Canada’s Ellesmere Island in the high Arctic.
最近，研究來自加拿大於高北極(加拿大地區，尤其是北極圈內的北部島嶼)埃爾斯米爾島之化石的科學家們，確認了兩種新的史前靈長類動物。
The primates are closely related and likely originated from a single colonisation event, following which they split into two species: Ignacius dawsonae and Ignacius mckennai.
這些靈長類動物是密切相關的，且很可能源自一次單一移棲事件。繼此之後，牠們分裂成兩物種：Ignacius mckennai及Ignacius dawsonae。
At 52 million years old, they represent the most recent known members of their genus.
在5200萬年前，牠們代表了其屬中，最新的已知成員。
The primates colonised the high latitudes during a period of historic global warming called the early Eocene climatic optimum (EECO). During this period, the high Arctic, now cold and inhospitable, had a climate similar to the cypress swamps of the southeastern USA. The primates shared the landscape with species that are today associated with warmer climates, including crocodilians and tapirs.
在被稱為始新世早期氣候最適宜時期(EECO)之歷史性全球變暖期間，這些靈長類動物移棲於高緯度地區。在此期間，目前寒冷且荒涼的高北極具有，類似美國東南部柏樹沼澤地的氣候。此些靈長類動物和當今，與較溫暖氣候相關(包括鱷魚及貘等)的物種共有此地帶。
This warmer period had a major impact on biodiversity. But it also has important implications for our understanding of climate change today. Human impact on the climate is so dramatic that scientists are calling for the acknowledgement of a new geological period called the Anthropocene.
該較溫暖時期，對生物多樣性具有重大影響。不過，就目前我們有關氣候變遷的理解而言，這也具有重要意涵。人類對氣候的影響如此顯著，以至於科學家們呼籲承認一個，被稱為人類世(或人新世)的新地質時期(也就是，用於描述地球歷史上，人類活動開始對地球氣候及生態系統，產生重大影響的最近時期)。
The Ellesmere Ignacius species are known only from teeth and jaw fragments. But other species of Ignacius for which additional skeletal materials are available indicate a tree-living lifestyle similar to modern colugos, a gliding mammal native to southeast Asia. The new primates likely evolved from ancestral paromomyids (extinct gliding primates) from North America’s southerly latitudes.
此些埃爾斯米爾島的Ignacius物種，僅從牙齒及頜骨碎片，被得知。不過，有關Ignacius，可取得之額外骨骼資料的其他物種，顯示了一種，類似現代鼯猴(colugos，一種原產於東南亞的滑翔哺乳動物)的樹棲生活方式。此些新靈長類動物很可能演化自，來自北美南緯地區的原種paromyids(已滅絕之滑翔的靈長類動物)。
圖1. 鼯猴(Colugo)，一種原產於東南亞的滑翔哺乳動物。
A Colugo, a gliding mammal native to southeast Asia.
Based on tooth size, Ignacius dawsonae at 1.17 kg was twice as large as Ignacius clarkforkensis, the biggest mid-latitude member of the genus (0.47 kg). Ignacius mckennai at 1.98 kg may have been four times as large as its biggest southern cousin. The new Ignacius were roughly the size of a rabbit.
根據牙齒大小，重1.17公斤的Ignacius dawsonae是該屬中，最大之中緯度地區成員Ignacius clarkforkensis (0.47公斤)的兩倍。重1.98公斤的Ignacius mckennai很可能曾是，其最大之南方同類的四倍。此些新的Ignacius，大約是兔子的大小。
These results support Bergmann’s Rule, a theory that links the climate to animal anatomy. It states that the colder the climate, the larger the animal. While the high Arctic was warmer during the EECO than it is today, its climate was still cooler than the ancestral range of Ignacius species.
此些研究結果支持了伯格曼法則，一種將氣候與動物結構聯繫起來(指同一種類恆溫動物的體形，會隨著生活地區緯度或海拔的增高而變大)的理論。其陳述，氣候愈冷，動物愈大。儘管在EECO期間，高北極比目前暖和。不過，其氣候仍然比Ignacius物種的原種分佈區域涼爽。
As a shape gets bigger, its relative surface area to volume ratio gets smaller. This means the surface area over which heat is lost is relatively smaller for larger animals. To minimise heat loss, animals that live in colder climates tend to be bigger than similar species in warmer climates.
由於形狀變大，其相對表面積對體積的比變得較小。這意味著，對於較大的動物而言，於此表面積上的熱量喪失，相對較少。為了使熱量喪失減至最少，棲息於較寒冷氣候中的動物，傾向比棲息於較溫暖氣候中，相似的物種較大。
Penguins, for example, broadly follow Bergmann’s rule. The large emperor penguin lives near the south pole, while smaller species such as the Humboldt penguin inhabit regions closer to the equator.
譬如，企鵝顯然遵循了伯格曼法則。大的帝王企鵝生活於南極附近，而諸如洪氏環企鵝的較小物種，則棲息於靠近赤道的地區。
The Ellesmere Ignacius also exhibits large teeth and jaw muscles. The biomechanics indicate a high bite force with relatively low and serrated molars. This suggests a diet that included harder objects such as seeds and nuts that provided a food source during the long dark winters of such northerly latitudes.
埃爾斯米爾島的Ignacius 也展現了，大的牙齒及顎肌肉。此些生物力學顯示，具有相對低且鋸齒狀之臼齒的高咬合力。這暗示了一種，包括在如北方緯度地區的漫長黑暗冬季，提供諸如種子及堅果等，較硬東西之食物來源的飲食。
圖2. 圖示為帝王企鵝(大的，南極)及洪氏環企鵝(小的，靠近赤道)。
Photo shows Emperor Penguin (large, Antarctic) and Humboldt Penguin (small, near equator).
The fossils were excavated at multiple locations over several decades before being examined and photographed using micro-computed tomography. This is a modern technique that allows scientists to digitally map the anatomy of fossils embedded inside rocks.
幾十年來，此些化石是在，被使用微電腦斷層掃描技術檢查及拍照前的幾十年間，於多個地點被挖掘出。這是一種，使科學家們得以數位式繪製，被嵌入岩石中之化石構造圖的現代技術。
圖3. Ignacius Dawsonae(5200萬年前，生活於北極高地之早期靈長類動物的親緣動物)之牙齒及頜骨碎片的微電腦斷層掃描圖像。
Micro-computed tomography images of the teeth and jaw fragments of Ignacius Dawsonae.
The researchers then conducted phylogenetic analysis of the teeth and jaw fragments to determine identity and evolutionary relatedness to previously described species. They also compared tooth topography (a 3D landscape map of the tooth surface) with living and other fossil primates to determine the new species’ likely diet.
之後，研究人員們進行了，此些牙齒及頜骨碎片之種系發生(是對一個物種或一組生物體或一個生物體之特定特徵的演化發展研究)的分析，來確認與先前所描述物種之身分及演化的相關性。他們也現有及其他成化石的靈長類動物，比較了牙齒表面狀態(牙齒表面的3D形狀)，以確定此些新物種的可能飲食。
The EECO will have seen a turnover of animal species. As local climates warm, individual organisms have two options: move or die. At the species level, animals have a third option, to evolve over generations to adapt to changing environmental conditions.
始新世早期氣候最適宜時期(EECO)可能曾經歷動物物種的轉移。隨著當地氣候變暖，個體生物有兩種選擇：遷移或死亡。在物種層面上，動物具有第三種選擇，即透過數代的演化，來適應變化中的環境條件。
The fact that mammals living in warmer climates colonised the changing Arctic habitat is likely because their own ancestral range was becoming too hot. This indicates the potential for migration, followed by evolutionary radiation, to fill opening ecological niches created by climate change.
生存於較溫暖氣候中的哺乳動物，移棲於變化中之北極棲息地的事實，很可能是因為其原種(祖先)的分佈區域變得太熱。這顯示了遷移的潛力，繼之而來的演化輻射(由物種形成率升高引起之分類學上多樣性的增加)，來填補因氣候變遷所創造的空缺生態位。
But the colonisation was selective. Several mammal species, including deer, antelope, horses and small herbivore groups lived in warmer regions further south but did not inhabit such northerly latitudes.
不過，移棲是選擇性的。包括鹿、羚羊、馬及小型食草動物群等，幾種哺乳動物生存於較南的較溫暖地區，而並不棲息於如此偏北的緯度地區。
A much greater variety of primitive primates also did not make Ellesmere their home during the EECO. Biodiversity in the High Arctic therefore remained lower than at more southerly latitudes.
在EECO期間，更多種類的原始靈長類動物，也沒有以埃爾斯米爾島為棲息地。因此，於高北極的生物多樣性仍然低於，較南的緯度地區。
The researchers suggest that temperature was not the main barrier to successful colonisation. Instead it was probably the long winter darkness and the resultant effect on the availability of plant materials as food. Some mammal species were not capable of the transition.
此些研究人員暗示，溫度並非成功移棲的主要障礙。反而可能是，漫長冬季的黑暗，及因而對作為食物之植物物資可用性發生的影響。有些哺乳動物物種沒有此變遷能力。
History shows us that various mammals can move northwards and adapt, and that biodiversity can increase. But evolution needs two things: genetic diversity and time.
歷史告知人們，各種的哺乳動物能向北遷移並適應，而且生物多樣性會增多。不過，演化需要兩件事：遺傳多樣性及時間。
However, expanding human populations are having increasingly destructive effects on nature. Persecution and habitat loss have, for example, reduced population sizes and genetic diversity across species. Pollution also means that the climate is changing faster than ever before. It is thus harder for species to adapt.
然而，擴大中的人口，正日益對大自然產生諸多破壞性影響。譬如，迫害及棲息地喪失，已經減少了種群規模及跨物種的遺傳多樣性。污染也意味著，氣候變遷正比以往任何時候更為快速。因此，對物種而言，這更難適應。
圖4. 氣候變遷正以比往昔任何時候更快中。
The climate is changing faster than ever before.
Ironically, climate change may also explain why the Arctic Ignacius species went extinct. As Arctic temperatures again cooled, Ignacius likely found itself maladapted to the cold and unable to migrate south or compete with mid-latitude species that were better adapted to their environment.
反諷的是，氣候變遷也能解釋，為何北極地區Ignacius物種的滅絕。當北極溫度再次變涼時，Ignacius很可能發現自身不適應寒冷，且無法向南遷移，或與是更佳適應其環境的中緯度物種競爭。
Humans cheat the climate by using technology to evade environmental challenges. Air conditioning, central heating and clothes enable humans to survive in places that we would otherwise be unable to tolerate. But we are vulnerable to climate change.
人類藉由使用技術以逃避環境的諸多挑戰，來躲避氣候。空調、中央供暖及衣服使人類能在，否則無法容忍的地方生存下來。不過，我們很容易受到氣候變遷的影響。
If human-induced climate change continues, it is not just other animals that will experience the same fate as Ignacius. We will too.
倘若人為引起的氣候變遷繼續下去，則不僅是其他動物會經歷，與Ignacius物種相同的命運。我們也會。
網址：https://theconversation.com/primates-colonised-the-arctic-during-a-period-of-ancient-global-warming-their-fate-offers-a-lesson-as-climate-change-speeds-up-198265
翻譯：許東榮
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