對地核成分的新見解

原文網址：www.sciencedaily.com/releases/2015/09/150922151604.htm

A new view of the content of Earth's core

對地核成分的新見解

There is more oxygen in the core of Earth than originally thought. Lawrence Livermore geologist Rick Ryerson and international colleagues discovered some new findings about Earth's core and mantle by considering their geophysical and geochemical signatures together. This research provides insight into the origins of Earth's formation.

地核的含氧量比原先所認為的還要高。勞倫斯利福摩爾國家實驗室的地質學家Rick Ryerson與其他國際研究人員統合了地函與地核的地球物理和地球化學訊號，而有了新發現。此研究有助於瞭解地球如何形成。

Based on the higher oxygen concentration of the core, Ryerson's team concludes that Earth must have accreted material that is more oxidized than the present-day mantle, similar to that of planetesimals such as asteroidal bodies. A planetesimal is an object formed from dust, rock and other materials and can be can be anywhere in size from several meters to hundreds of kilometers.

Ryerson的團隊根據較高的地核含氧量推測，吸積(accrete)成地球的原料擁有比現今地函還要高的氧化程度，可能與小行星之類的微行星(planetesimal)相似。微行星是由塵埃、岩石或者其他物質所組成的星體，大小可從數公尺到上百公里不等。

Earth formed about 4.56 billion years ago over a period of several tens of millions of years through the accretion of planetary embryos and planetesimals. The energy delivered by progressively larger impacts maintained Earth's outer layer and an extensively molten magma ocean. Gravitational separation of metal and silicate within the magma ocean results in the planet characterized by a metallic core and a silicate mantle.

地球經歷了數千萬年的行星胚與微行星加積過程後，約在45.6億年前形成。越發強勁的撞擊所傳遞出來的能量使得地球外層變成一片浩瀚無垠的岩漿海。發生在其中的重力分離作用分離了金屬與矽酸鹽，造成地球的地核與地函分別由金屬和矽酸鹽組成。

The formation of Earth's core left behind geophysical and geochemical signatures in the core and mantle that remain to this day. In the past, core formation models have only attempted to address the evolution of core and mantel compositional signatures separately rather than looking for a joint solution.

在這過程中刻劃於地核和地函的地球物理與地球化學訊號，我們時至今日仍能偵測的到。過去的地核形成模型在瞭解地核與地函的成分如何演變時，是將它們分開處理，而非將兩者視為一個聯合體系。

By combining experimental petrology, geochemistry, mineral physics and seismology, the team found that core formation occurred in a hot (liquid) moderately deep magma ocean not exceeding 1,800-kilometer depth, under conditions more oxidized than present-day Earth.

結合了實驗岩石學、地球化學、礦物物理學和地震學，研究團隊發現地核形成於一座炎熱(液態)、深度適中而不超過1800公里深的岩漿海，環境中氧化程度較目前的地球要高。

"This new model is at odds with the current belief that core formation occurred under reduction conditions," Ryerson said. "Instead we found that Earth's magma ocean started out oxidized and has become reduced through time by oxygen incorporation into the core."

「這個新模型的奇特之處在於它與目前認為地核形成於還原環境下的說法相悖。」Ryerson說。「反之，我們發現地球的岩漿海在形成時處於氧化態，隨著時間流逝，氧慢慢的與地函結合，造成岩漿海越趨還原。」

They found the oxygen concentrations in the core are higher than previously thought and silicon concentrations are lower than previous estimates.

他們發現與之前的預測相比，地核的氧含量較高而矽酸鹽含量則較低。

引用自：DOE/Lawrence Livermore National Laboratory. "A new view of the content of Earth's core." ScienceDaily. ScienceDaily, 22 September 2015. 

包含230萬個物種的「生命之樹」

原文網址：www.sciencedaily.com/releases/2015/09/150918180310.htm

'Tree of life' for 2.3 million species released

包含230萬個物種的「生命之樹」

Large, open-access resource aims to be 'Wikipedia' for evolutionary history

以成為演化史「維基百科」為目標的大型公開資源

A first draft of the "tree of life" for the roughly 2.3 million named species of animals, plants, fungi and microbes -- from platypuses to puffballs -- has been released.

首幅包含約230萬個已命名的動物、植物、真菌和微生物的生命之樹草圖已經公布，包括了從鴨嘴獸至馬勃菌(puffball)在內的種種生命。

A collaborative effort among eleven institutions, the tree depicts the relationships among living things as they diverged from one another over time, tracing back to the beginning of life on Earth more than 3.5 billion years ago.

由11所研究機構合作建立而成的這棵生命之樹，呈現出從35億年前地球生命起源開始，隨著時間推進，生物逐漸從另一生物分歧出來而開枝散葉的過程中，彼此之間的關係。

Tens of thousands of smaller trees have been published over the years for select branches of the tree of life -- some containing upwards of 100,000 species -- but this is the first time those results have been combined into a single tree that encompasses all of life. The end result is a digital resource that available free online for anyone to use or edit, much like a "Wikipedia" for evolutionary trees.

在過去的數年間，科學界已經發表了數以萬計較小株，僅呈現特定分枝的生命之樹。雖然有些包含了多達100000種以上的生物，但這是第一次有人將這些成果全部合併，而繪出容納所有物種的單一生命樹。最終結果為在網路上公開，可讓任何人免費使用或者編輯的數位化資源，就像是維基百科的演化樹版本。

"This is the first real attempt to connect the dots and put it all together," said principal investigator Karen Cranston of Duke University. "Think of it as Version 1.0."

「這是科學家實際上首次嘗試將這些點全部連起來並拼湊出完整的圖像。」計畫主持人，杜克大學的Karen Cranston說，「可以將之視作為版本1.0。」

The current version of the tree -- along with the underlying data and source code -- is available to browse and download at https://tree.opentreeoflife.org.

這棵樹的現行版本、數據來源和原始程式碼，都可以在https://tree.opentreeoflife.org中瀏覽與下載。

It is also described in an article appearing Sept. 18 in the Proceedings of the National Academy of Sciences.

9月18日刊登於《美國國家科學院期刊》的文章中也會詳述這棵生命之樹。

Evolutionary trees, branching diagrams that often look like a cross between a candelabra and a subway map, aren't just for figuring out whether aardvarks are more closely related to moles or manatees, or pinpointing a slime mold's closest cousins. Understanding how the millions of species on Earth are related to one another helps scientists discover new drugs, increase crop and livestock yields, and trace the origins and spread of infectious diseases such as HIV, Ebola and influenza.

演化樹是一種有許多分枝的圖表，往往看起來像是分枝眾多的燭臺和地鐵路線圖之間的混合體。它的用途不只是找出鼴鼠和海牛誰跟土豚的關係比較近；或者指出誰是粘菌關係最近的表親。瞭解地球上數以百萬計物種彼此之間的關聯，有助於科學家研發新型藥物、增加農業和畜牧業產量，並找出傳染性疾病，像是愛滋病、伊波拉病毒和流感的起源與散播路徑。

Rather than build the tree of life from scratch, the researchers pieced it together by compiling thousands of smaller chunks that had already been published online and merging them together into a gigantic "supertree" that encompasses all named species.

研究人員並非一點一滴地樹立起這棵大樹，而是收集數千條發表在網路上的枝幹，將它們拼拼湊湊，接合成這棵容納所有已命名物種的「神木」。

The initial draft is based on nearly 500 smaller trees from previously published studies.

他們利用發表於過往研究中，將近500株的小型演化樹來建立最初的圖樣。

To map trees from different sources to the branches and twigs of a single supertree, one of the biggest challenges was simply accounting for the name changes, alternate names, common misspellings and abbreviations for each species. The eastern red bat, for example, is often listed under two scientific names, Lasiurus borealis and Nycteris borealis. Spiny anteaters once shared their scientific name with a group of moray eels.

考量到每一個物種名字的變化、別名、常見拼字錯誤和縮寫，要從來自四面八方的資料繪製出這棵神木的一根分枝甚至末梢，便是一大挑戰。拿東方紅蝠(eastern red bat)為例，牠在學名上就有兩種稱呼，Lasiurus borealis和Nycteris borealis。而針鼴則曾經與一種鯙類(海鱔)共用學名。

"Although a massive undertaking in its own right, this draft tree of life represents only a first step," the researchers wrote.

「儘管我們為此已嘔心瀝血，這幅生命之樹草圖仍然只是相當初步的成果。」研究人員寫道。

For one, only a tiny fraction of published trees are digitally available.

原因之一是已發表的演化樹中，只有一小部份能以數位化的形式取得。

A survey of more than 7,500 phylogenetic studies published between 2000 and 2012 in more than 100 journals found that only one out of six studies had deposited their data in a digital, downloadable format that the researchers could use.

在調查了從2000至2012年發表在超過100種期刊中，7500篇以上有關親緣關係的研究後，他們發現當中大概只有六分之一有數位化他們的數據，成為可供其他研究人員下載的格式。

The vast majority of evolutionary trees are published as PDFs and other image files that are impossible to enter into a database or merge with other trees.

絕大部分的演化樹是以PDF或其他影像檔的格式發表，而這類格式並無法輸入資料庫或是合併至其餘演化樹。

"There's a pretty big gap between the sum of what scientists know about how living things are related, and what's actually available digitally," Cranston said.

「科學家全體對現存生物彼此之間關聯的所有相關知識中，能以數位化形式取得的部分實則少之又少。」Cranston說。

As a result, the relationships depicted in some parts of the tree, such as the branches representing the pea and sunflower families, don't always agree with expert opinion.

因此，呈現在這棵生命之樹中的部分親緣關係，像是豌豆與向日葵家族所在分枝的樣貌，並非總是符合其他專家的意見。

Other parts of the tree, particularly insects and microbes, remain elusive.

至於其他一些部分仍然混沌不清，尤其是代表昆蟲和微生物的分枝。

That's because even the most popular online archive of raw genetic sequences -- from which many evolutionary trees are built -- contains DNA data for less than five percent of the tens of millions species estimated to exist on Earth.

即便是科學家在建構許多演化樹時最常使用的原始基因序列網路資料庫，其含有的DNA資料估計也不到現存於地球上的數千萬種生物中的5%。

"As important as showing what we do know about relationships, this first tree of life is also important in revealing what we don't know," said co-author Douglas Soltis of the University of Florida.

「第一棵生命之樹的重要之處在於它顯現出我們對這些親緣關係所知多少，而同樣重要的是它也呈現了我們未知的部分。」共同作者，佛羅里達大學的Douglas Soltis說。

To help fill in the gaps, the team is also developing software that will enable researchers to log on and update and revise the tree as new data come in for the millions of species still being named or discovered.

由於還有數百萬筆仍在命名或尚待發現的物種的新資料會來填補這些空缺，團隊也設計出可以讓其他研究人員登入、更新並持續審查這棵生命之樹的軟體。

"It's by no means finished," Cranston said. "It's critically important to share data for already-published and newly-published work if we want to improve the tree."

「這絕不是個結束，」Cranston說，「若我們想要繼續改良並優化這棵生命之樹，至關重要的是分享已經發表的數據，以及新刊出的成果。」

"Twenty five years ago people said this goal of huge trees was impossible," Soltis said. "The Open Tree of Life is an important starting point that other investigators can now refine and improve for decades to come."

「25年前人們會說要創建一株這麼雄偉的演化樹是痴人說夢，」Soltis說，「「開放的生命之樹」是個重要的開始，未來數十年其他研究人員將會繼續讓它變得更加完備且精確。」

This research was supported by a three-year, $5.76 million grant from the U.S. National Science Foundation (1208809).

美國國家科學基金會給予此研究3年總計576萬美元的贊助(編號：1208809)。

This circular family tree of Earth's lifeforms is considered a first draft of the 3.5-billion-year history of how life evolved and diverged.

此幅呈現環形，包含所有地球生命的家族樹為首張草圖繪出35億年來，地球生命如何演化與分枝。

(Metazoa：動物；Archaea：古菌；Bacteria：細菌；Excavata：古蟲；Amoebozoa：變形蟲；SAR：SAR超類群；Archaeplastida：原始色素體生物(泛植物)；Fungi：真菌)

來源：opentreeoflife.org

引用自：Duke University. "'Tree of life' for 2.3 million species released: Large, open-access resource aims to be 'Wikipedia' for evolutionary history." ScienceDaily. ScienceDaily, 18 September 2015. 

 

發現有著小腦袋的人類祖先

原文網址：www.sciencedaily.com/releases/2015/09/150910084610.htm

Ancient ancestor of humans with tiny brain discovered

發現有著小腦袋的人類祖先

Homo naledi raises intriguing questions about our evolutionary past

納勒迪(naledi)人激起了一些關於我們過往演化歷程的有趣問題

An international team of scientists, including one from the University of Colorado Denver and another from the University of Colorado Anschutz Medical Campus in Aurora, announced the discovery Thursday of a new species of hominin, a small creature with a tiny brain that opens the door to a new way of thinking about our ancient ancestors.

包括兩名分別來自科羅拉多大學丹佛分校，與科羅拉多大學安舒茨醫學校區的國際科學家團隊，於週四發表了他們發現的新種人族化石。這些身型矮小且腦袋不大的化石，讓科學家對我們的老祖宗有了嶄新的想法。

The discovery of 15 individuals, consisting of 1,550 bones, represents the largest fossil hominin find on the African continent.

此次發現為非洲大陸出土的最大一批人族(hominin)化石，包含了15具人類骨骸，總計1550塊骨頭。

"We found adults and children in the cave who are members of genus Homo but very different from modern humans," said CU Denver Associate Professor of Anthropology. Charles Musiba, PhD, who took part in a press conference Thursday near the discovery inside the Rising Star Cave in the Cradle of Humankind World Heritage Site outside Johannesburg, South Africa. "They are very petite and have the brain size of chimpanzees. The only thing similar we know of are the so-called `hobbits' of Flores Island in Indonesia."

「我們在洞窟中發現的成人和孩童化石雖然隸屬於人屬(Homo)，但他們跟現代人的差異相當大。」在記者會上，科羅拉多大學丹佛分校人類學系的副教授Charles Musiba博士說。記者會週四舉辦在發現這些化石的「啟星洞」(Rising Star Cave)附近。此洞穴位於南非約翰尼斯堡外，人類的搖籃世界遺址(Cradle of Humankind World Heritage Site)中。「他們的個頭十分嬌小，腦容量與黑猩猩相仿。就我們所知，唯一跟他們相似的物種為發現於印尼弗洛勒斯島的「哈比人」。」

Homo floresiensis or Flores Man was discovered in 2003. Like this latest finding, it stood 3.5 five feet high and seems to have existed relatively recently though the exact age is unknown.

佛羅勒斯人(Homo floresiensis)發現於2003年。就像這件最新發現，佛羅勒斯人站起來的高度僅3.5呎(約1公尺)，生存年代雖然尚未確定，但可能相當接近現代。

Caley Orr, PhD, an assistant professor of cell and developmental biology at the University of Colorado School of Medicine, analyzed the fossil hands.

科羅拉多大學醫學校區，細胞與發育生物學系的助理教授Caley Orr博士分析了這些化石的手部。

"The hand has human-like features for manipulation of objects and curved fingers that are well adapted for climbing," Orr said. "But its exact position on our family tree is still unknown."

「他們的手掌跟人類一樣具有可以抓握物體的能力，而彎曲的手指則顯示他們為攀爬高手。」Orr說，「但我們仍不清楚他們在人類族譜中的確切地位。」

The new species has been dubbed Homo naledi after the cave where it was found -- naledi means `star' in the local South African language Sesotho.

此新物種目前以發現它們的洞窟為名，稱作納勒迪(naledi)人。在南非當地的塞索托(Sesotho)語當中，「納勒迪」的意思是「星星」。

One of the most intriguing aspects of the discovery is that the bodies appear to have been deposited in the cave intentionally. Scientists have long believed this sort of ritualized or repeated behavior was limited to humans.

這起發現中最令人感興趣的地方之一，是這些遺骸似乎刻意被堆積在這個洞穴中。科學家一般相信僅有人類會表現出這種儀式性或重複性地行為。

The team of 35 to 40 scientists was led by Lee Berger, research professor in the Evolutionary Studies Institute at the University of Witwatersrand in South Africa. It was supported by the National Geographic Society and the National Research Foundation. The October issue of National Geographic magazine will feature the discovery as its cover story. It will also be the subject of a NOVA/National Geographic Special airing Sept. 16.

這個35至40人的科學家團隊由Lee Berger領導，其為南非金山大學演化學研究所的研究教授，並由國家地理學會與國家研究基金會贊助。國家地理雜誌10月號將會以這項發現做為封面故事；國家地理頻道也會在9月16號播映以此為主題的特別節目。

Getting inside the Dinaledi chamber of the remote cave system was difficult, requiring the help of six `underground astronauts,' who squeezed through a 7-inch wide gap to reach the remains.

要經由罕為人至的地道系統進入迪納勒迪洞穴是相當困難的，這需要六名「地底太空人」的協助，他們能通過7英吋(18公分)窄的岩縫而抵達那些骸骨的所在位置。

"The chamber has not given up all of its secrets," said Berger, a National Geographic Explorer-in-Residence. "There are potentially hundreds if not thousands of remains of H. naledi still down there."
「這座洞穴還沒吐露它所有的秘密，」國家地理雜誌駐會探險家Berger說。「就算沒有數千具，也可能還有數百具的納勒迪人遺骸仍在其中。」

The announcement coincides with the publication of two studies about the new species in the journal eLife, co-authored by Musiba and Orr.

與此聲明同一時間發表的為討論此新物種，刊載於期刊《eLife》上的兩篇論文，共同作者包括了Musiba 和Orr。

In it, the researchers try to place Homo naledi in context with other species. Generally speaking, they say, there is an assumption that any new group of fossils must belong to an existing species.

在論文中，研究人員試圖將納勒迪人歸類為其他的物種。他們說，一般而言都會推測新發現的化石群屬於已知的物種。

But it's not that simple here.

但這次的情況並不那麼簡單。

"Assigning these remains to any known species of Homo is problematic," the study said. "While Homo(naledi) shares aspects of cranial and mandibular morphology with Homo habilis, Homo rudolfensis, Homo erectus, MP Homo and Homo sapiens, it differs from all of these taxa in its unique combination of derived cranial vault, maxillary, and mandibular morphology."

「要將這些骸骨歸類至任何已知的人屬物種可說困難重重。」論文中寫道，「雖然此(納勒迪)人屬的頭蓋骨和下顎形貌與巧人(Homo habilis)、盧多爾夫人(Homo rudolfensis)、直立人(Homo erectus)、中更新世人(MP Homo)及智人(Homo sapiens)皆有相似之處，他的顱頂、上頷與下顎組合起來的型態卻跟這些人種大相逕庭。」

The study suggests that Homonaledi most closely resembles Homoerectus with its small brain and body size. Yet it also resembles Australopithecus which highlights its own uniqueness.

研究認為與納勒迪人最相近的物種為直立人，因兩者體型和腦容量都很小；然而納勒迪人的獨特之處在於他也跟南方古猿十分相似。

Complicating matters is the fact that researchers still don't know the exact age of the fossil site.

讓情況更錯綜複雜的是研究人員無法得知這座化石遺址的確切年代。

"If these fossils are late Pliocene or early Pleistocene, it is possible that this new species of small-brained, early Homo represents an intermediate between Australopithecus and Homoerectus," the study said.

「如果這些化石的年代為晚上新世或早更新世，那麼這些小腦袋的早期人屬新物種，可能就代表了南方古猿與直立人之間的過渡型態。」研究表示。

That would also make the new species very old.

這也代表說這個新物種的年代相當古老。

But if the fossils are more recent, they theorize, it raises the possibility that a small-brained Homo lived in southern Africa at the same time as larger brained Homo species were evolving.

然而，他們推論若這些化石更接近現代，就很可能代表在南非的人屬演化出擁有較大腦容量的物種時，這些腦容量小的人屬也跟他們同時生活在一塊。

"This raises many questions," Musiba said. "How many species of human were there? Were their lines that simply extended outward and then disappeared? Did they co-exist with modern humans? Did they interbreed?"

「這激發了許多疑問，」Musiba說。「當時這個地方到底有多少種人屬？他們是否未產生任何後裔然後就默默消失了？他們有跟現代人共同在一起生活過嗎？甚至曾互相混血？」

Homo naledi has a chest similar to a chimpanzee and hands and feet proportionate with modern humans, though with curved fingers.

納勒迪人的胸腔構造與黑猩猩相似，而手腳比例則與現代人相仿，儘管他們的指頭是彎曲的。

"They would have had great climbing ability," said Musiba. "The oldest adults were about 45 and the youngest were infants."

「他們是相當厲害的攀爬能手，」Musiba說。「年紀最老的成人約莫45歲，而最小的還是嬰兒。」

He described poring over the bones late at night as akin to `hitting the jackpot.'

他形容在深夜鑽研那些骨骸時的感覺簡直像是「中了樂透頭獎」。

"You just didn't want to go home because it was so exciting," he said. "I felt like a kid in a candy store." The find represents another milestone in Musiba's efforts to advance the understanding of our earliest human relatives.

「欣喜若狂到完全不想回家，」他說。「我就像是個走進糖果屋的男孩。」在Musiba致力瞭解人類最早期近親的生涯中，這是另一個里程碑。

As director of CU Denver's Tanzania Field School, he takes groups of students each year to gain hands-on experience working in and around the famed Laetoli hominin footprints site and Olduvai Gorge where some of the oldest hominin remains have been found.

身為科羅拉多大學丹佛分校坦尚尼亞田野學校的主任，他每年都會帶學生進行實地考察。地點包括了著名的雷托里(Laetoli)人類腳印遺址，和曾發現幾具最早人類化石的奧杜威峽谷(Olduvai Gorge)之內或周遭地區。

Not long ago, they discovered ancient footprints of lions, rhinos and antelopes near those of the early hominins.

不久之前，他們在早期人類腳印旁發現了獅子、犀牛與羚羊留下來的遠古足跡。

And last year, Musiba was appointed to an international team of advisors dedicated to building a museum complex in Tanzania to showcase a collection of 70 hominin footprints, estimated at 3.6 million years old. They are considered the earliest example of bipedalism among hominins.

而在去年，Musiba被委任至一國際顧問團，協助成立位於坦尚尼亞的一座博物館大樓，預計要展示估計年代為360萬年前，多達70件的人類足跡收藏品。這些足跡被認為是人類以雙足行走的最早案例。

Musiba said the Rising Star expedition was notable for getting so many anthropologists to work together.

Musiba說在探索遠征啟星洞的過程中，令他印象深刻的是與許多人類學家共事。

"Anthropology can be a cut-throat profession with all these scientists scrambling for limited resources," he said. "To me one of the most exciting aspects of this research was the collaborative nature of it."

「有時人類學是相當殘酷的，因為所有的研究人員都想要爭取那有限的資源。」他說，「對我而言，這項研究最令人振奮之處在於它是建立在眾人合作的基礎上。」

更多圖片可以看Homo naledi - Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Homo_naledi

引用自：University of Colorado Anschutz Medical Campus. "Ancient ancestor of humans with tiny brain discovered: Homo naledi raises intriguing questions about our evolutionary past." ScienceDaily. ScienceDaily, 10 September 2015.