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Searching For Earth’s Oldest Life
Have you wondered why it is scientists have concluded that our planet is billions of years old?
Sedimentary Fossils
One of the reasons is what researchers have discovered studying the remains of past life preserved in rocks, particularly sedimentary rocks. These rocks are formed from particles of mud and sand, typically when they settle to the bottom of a body of water. Fossils of organisms with hard body parts don’t appear in sedimentary rock older than about 600 million years, but the Earth is estimated to be 4.6 billion years old.
To find the oldest life, paleontologists looked for it in the oldest sedimentary rock they could find. Sedimentary rocks dating back to Earth’s earliest days are rare. Some of the oldest known are about three and a half billion years old.
Stromatolites
In these very old rocks, paleontologists have found something that looked familiar. Certain communities of microbes can form layered, rock-like mounds called stromatolites. Stromatolites grow in shallow bodies of water in many places around the world. In the 1980′s paleontologists found the remains of ancient stromatolites in 3.5 billion year old sedimentary rocks.
Besides stromatolites, possible microscopic fossils have been found in rocks up to 3.5 billion years old. While the origin of these tiny structures is still intensely debated, many scientists are convinced that they are the remains of microorganisms. It appears that by at least 3.5 billion years ago, the oceans were teeming with life, and that the land was also colonized by microbes very early in Earth’s
你有沒有想過為什么科學(xué)家會(huì)認(rèn)為地球已經(jīng)有數(shù)十億年的歷史了？
沉積化石
理由之一便是研究人員在研究巖石特別是沉積巖中保存著的生物遺骸時(shí)找到了證據(jù)。這些巖石是由泥土和沙礫沉積在水底形成的。生物體中較硬的身體部分所形成的化石不會(huì)出現(xiàn)在6億年以上的沉積巖中，但是地球預(yù)計(jì)已經(jīng)有46億年之久了。
為了尋找最古老的生命，古生物學(xué)者找到了他們可以找到的最古老的沉積巖。這些可以追溯到形成于地球初期的沉積巖是十分罕見的。目前所知的一些最古老的沉積巖大約有35億年的歷史。
疊層石
在這些古老的巖石中，古生物學(xué)者發(fā)現(xiàn)了一些熟悉的東西。某些菌落可以形成一層一層，巖石狀的土丘，被叫做疊層石。世界上有很多地方的淺水區(qū)都存在著疊層石。在20世紀(jì)80年代的時(shí)候，古生物學(xué)家在35億年的沉積巖里發(fā)現(xiàn)了古疊層石的遺骸。
除了疊層石外，其他目前在巖石中已經(jīng)找到的可能的微觀化石已經(jīng)有長達(dá)35億年的歷史了。雖然關(guān)于這些微小結(jié)構(gòu)的起源還存在著嚴(yán)重的分歧，但很多科學(xué)家已經(jīng)確認(rèn)，他們是微生物的殘骸。似乎在地球演變的早期過程中，至少在35億年以前，海洋里存在著大量生體命，而陸地是微生物的主要棲息地。
【本譯文由普特網(wǎng)友 kevinde 提供】
PS：西澳大利亞皮爾巴拉地區(qū)發(fā)現(xiàn)了至今為止最久遠(yuǎn)的生命證據(jù)。美國與澳大利亞的研究者們?cè)谄柊屠某练e巖中，發(fā)現(xiàn)了距今約34.5億年前的復(fù)雜的細(xì)菌生態(tài)系統(tǒng)的痕跡。這項(xiàng)發(fā)現(xiàn)又將地球上的生命證據(jù)提前了數(shù)百萬年。微生物和細(xì)菌喜歡集群生活，人類胃里的細(xì)菌群就是一例。細(xì)菌會(huì)根據(jù)環(huán)境中不同的化學(xué)梯度分層次生活，例如喜歡光的細(xì)菌生活在上層，而厭光的生活在下層。皮爾巴拉地區(qū)有著地球上最古老且最無損的沉積巖，研究者們?cè)谶@些沉積巖中發(fā)現(xiàn)了菌群的痕跡。35億年前的地球和現(xiàn)在差別很大，氣溫和海平面都遠(yuǎn)高于今天的水平。在更復(fù)雜的生命形式被進(jìn)化出來前，諸如皮爾巴拉地區(qū)的菌群這樣的細(xì)菌是地球上最為先進(jìn)的生命形式，它們對(duì)地球的統(tǒng)治長達(dá)十多億年。那時(shí)，地球上多數(shù)是海洋，火山活動(dòng)頻繁，空氣中充滿硫磺。而直到25億年前，真核生物才剛剛開始進(jìn)化出來，然后再經(jīng)過漫長的歲月，才進(jìn)化出多細(xì)胞生物直至動(dòng)物和人類?！犊茖W(xué)公園》
Searching For Earth’s Oldest Life
Have you wondered why it is scientists have concluded that our planet is billions of years old?
Sedimentary Fossils
One of the reasons is what researchers have discovered studying the remains of past life preserved in rocks, particularly sedimentary rocks. These rocks are formed from particles of mud and sand, typically when they settle to the bottom of a body of water. Fossils of organisms with hard body parts don’t appear in sedimentary rock older than about 600 million years, but the Earth is estimated to be 4.6 billion years old.
To find the oldest life, paleontologists looked for it in the oldest sedimentary rock they could find. Sedimentary rocks dating back to Earth’s earliest days are rare. Some of the oldest known are about three and a half billion years old.
Stromatolites
In these very old rocks, paleontologists have found something that looked familiar. Certain communities of microbes can form layered, rock-like mounds called stromatolites. Stromatolites grow in shallow bodies of water in many places around the world. In the 1980′s paleontologists found the remains of ancient stromatolites in 3.5 billion year old sedimentary rocks.
Besides stromatolites, possible microscopic fossils have been found in rocks up to 3.5 billion years old. While the origin of these tiny structures is still intensely debated, many scientists are convinced that they are the remains of microorganisms. It appears that by at least 3.5 billion years ago, the oceans were teeming with life, and that the land was also colonized by microbes very early in Earth’s
你有沒有想過為什么科學(xué)家會(huì)認(rèn)為地球已經(jīng)有數(shù)十億年的歷史了？
沉積化石
理由之一便是研究人員在研究巖石特別是沉積巖中保存著的生物遺骸時(shí)找到了證據(jù)。這些巖石是由泥土和沙礫沉積在水底形成的。生物體中較硬的身體部分所形成的化石不會(huì)出現(xiàn)在6億年以上的沉積巖中，但是地球預(yù)計(jì)已經(jīng)有46億年之久了。
為了尋找最古老的生命，古生物學(xué)者找到了他們可以找到的最古老的沉積巖。這些可以追溯到形成于地球初期的沉積巖是十分罕見的。目前所知的一些最古老的沉積巖大約有35億年的歷史。
疊層石
在這些古老的巖石中，古生物學(xué)者發(fā)現(xiàn)了一些熟悉的東西。某些菌落可以形成一層一層，巖石狀的土丘，被叫做疊層石。世界上有很多地方的淺水區(qū)都存在著疊層石。在20世紀(jì)80年代的時(shí)候，古生物學(xué)家在35億年的沉積巖里發(fā)現(xiàn)了古疊層石的遺骸。
除了疊層石外，其他目前在巖石中已經(jīng)找到的可能的微觀化石已經(jīng)有長達(dá)35億年的歷史了。雖然關(guān)于這些微小結(jié)構(gòu)的起源還存在著嚴(yán)重的分歧，但很多科學(xué)家已經(jīng)確認(rèn)，他們是微生物的殘骸。似乎在地球演變的早期過程中，至少在35億年以前，海洋里存在著大量生體命，而陸地是微生物的主要棲息地。
【本譯文由普特網(wǎng)友 kevinde 提供】
PS：西澳大利亞皮爾巴拉地區(qū)發(fā)現(xiàn)了至今為止最久遠(yuǎn)的生命證據(jù)。美國與澳大利亞的研究者們?cè)谄柊屠某练e巖中，發(fā)現(xiàn)了距今約34.5億年前的復(fù)雜的細(xì)菌生態(tài)系統(tǒng)的痕跡。這項(xiàng)發(fā)現(xiàn)又將地球上的生命證據(jù)提前了數(shù)百萬年。微生物和細(xì)菌喜歡集群生活，人類胃里的細(xì)菌群就是一例。細(xì)菌會(huì)根據(jù)環(huán)境中不同的化學(xué)梯度分層次生活，例如喜歡光的細(xì)菌生活在上層，而厭光的生活在下層。皮爾巴拉地區(qū)有著地球上最古老且最無損的沉積巖，研究者們?cè)谶@些沉積巖中發(fā)現(xiàn)了菌群的痕跡。35億年前的地球和現(xiàn)在差別很大，氣溫和海平面都遠(yuǎn)高于今天的水平。在更復(fù)雜的生命形式被進(jìn)化出來前，諸如皮爾巴拉地區(qū)的菌群這樣的細(xì)菌是地球上最為先進(jìn)的生命形式，它們對(duì)地球的統(tǒng)治長達(dá)十多億年。那時(shí)，地球上多數(shù)是海洋，火山活動(dòng)頻繁，空氣中充滿硫磺。而直到25億年前，真核生物才剛剛開始進(jìn)化出來，然后再經(jīng)過漫長的歲月，才進(jìn)化出多細(xì)胞生物直至動(dòng)物和人類?！犊茖W(xué)公園》