地球上での生命の証拠は,3800億年前より以前に存在していた
S J Mojzsis1, G Arrhenius, K D McKeegan
1Scripps Institution of Oceanography, University of California San Diego, La Jolla 92093-0220, USA. smojzsis@ucsd.edu
Nature
|November 7, 1996
まとめ
証拠によると,地球上の生命は少なくとも3億8000万年前に誕生した. 古代の岩石の地化学分析は,微生物化石の証拠より前の生物学的活動を示す軽い炭素同位体を示しています.
科学分野:
- 地質化学 地質化学
- パレオバイオロジーの古生物学
- 初期の地球科学 初期の地球科学
背景:
- 地球上の生命の起源の正確なタイミングは不明のままです.
- 微生物化石は初期の生命の証拠を提供しているが,古代の変形した岩で破壊されることが多い.
- 耐性ミネラルの地化学的シグネチャは,初期の生物学的活動を示す証拠を見つけるのに不可欠です.
研究 の 目的:
- 3億5千万年前に生命が誕生したという地化学的証拠を調査する.
- 古代アパタイト粒子の炭素同位体組成を分析するために.
- 観察された同位体シグネチャをアビオティックプロセスで説明できるかどうかを判断する.
主な方法:
- 炭素同位体組成のイオンマイクロプローブ測定.
- アパタイト粒子の内部にある炭酸性含有物の分析.
- 西グリーンランドとアキリア島からの古代帯状鉄の形成物の調査.
主要な成果:
- 3800万年,あるいはそれより古いアパタイト粒子のインクルージョンに含まれる炭素は,同位体的に軽い.
- この軽い炭素シグネチャーは,生物学的活性を示すものです.
- 観察された同位体組成と,アパタイトに選択的に組み込まれる原因は,既知の無生物学的プロセスでは説明できない.
結論:
- この発見は,少なくとも3億8000万年前に地球上に生命が誕生した証拠を提供する.
- 地化学データは,マイクロ化石記録のみに基づいた以前の仮定に異議を唱える.
- 未知の非生物学的プロセスを排除するために,さらなる研究が必要になる可能性があります.
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