The oldest trace of life was found in a rock that existed 3,900 million years ago

Recently the NHK News On-line reported the following:

世界最古の生命痕跡を発見 ３９億年前の岩石から

9月28日 5時52分

東京大学などの研究グループが、カナダで採取した３９億年前の岩石から、世界最古とみられる生命の痕跡を発見したと発表しました。

東京大学の小宮剛准教授などの研究グループは、カナダ北東部のラブラドル半島にあったおよそ３９億５０００万年前の岩石を採取し詳しく調べました。

その結果、自然界に存在する３種類の重さの炭素のうち、生物の体内に多い、最も軽い炭素の割合が高い塊が見つかり、研究グループでは、生物の死骸の痕跡だとしています。

これまでに確認された世界最古の生命の痕跡は、グリーンランドでみつかった３８億年前のものですが、今回の発見は、それよりも１億年以上古いものだということです。

地球は今からおよそ４５億年あまり前に誕生したと考えられていますが、生命がいつどのように誕生したのかはまだよくわかっていません。研究グループでは、地球にあらわれた初期の生命がどのような姿をしていたかを知る貴重な資料だとして、今後、生命の種類について特定を進めることにしています。

東京大学の小宮准教授は「痕跡の大きさは数十マイクロメートルで、細胞内に核をもたない原始的な生物だとみられる。泥が積もってできた岩石から出てきたので、海に生息していたのではないかと考えられるが、初期の生命がどのような姿をしていたのか解明したい」と話しています。

My translation

It was announced that a study group from the University of Tokyo had found a trace of the life that could be judged as the world oldest from a rock 3,900 million years old picked up in Canada.

A study group consisted of Takeshi Komiya associate professor of the University of Tokyo  and others had dug out a rock that was approximately 3,950 million years old at the Labrador peninsula in the Canada’s northeast and studied it carefully.

As a result, a block with a high percentage of the lightest type of carbon was found, a lot of this carbon could be found in the body of a creature. It was one of the 3 kinds of carbon that existed in the natural world that was differentiated by weight. It was assumed by the study group that it was the trace of a dead body of some creature.

So far the trace of oldest confirmed life in world was the one that was 3,800 million years old found in Greenland, it’s said that the present discovery was 100 million years older.

It was thought that the earth was formed about approximately 4,500 million years from now, but when did life was born was not quite known. To this study group, to know how early stage life appeared on earth was valuable data, from now on it would move forward to specify the different types of life.

Komiya associate professor of the University of Tokyo said that “the size of the trace is judged to be tens of micrometers; it seems to be a primitive creature without nucleus in the cell. Mud gathered together and turned into this rock, so I can judge that it might be living in a sea. I'd like to elucidate how early stage of life could look like."

    This discovery is important in knowing the beginning of life on earth.