Planavsky Noah J, Cole Devon B, Isson Terry T, Reinhard Christopher T, Crockford Peter W, Sheldon Nathan D, Lyons Timothy W
Department of Geology and Geophysics, Yale University, New Haven, CT, U.S.A.
NASA Astrobiology Institute Alternative Earths Team, Riverside, CA, U.S.A.
Emerg Top Life Sci. 2018 Sep 28;2(2):149-159. doi: 10.1042/ETLS20170161.
The oxygenation of the atmosphere - one of the most fundamental transformations in Earth's history - dramatically altered the chemical composition of the oceans and provides a compelling example of how life can reshape planetary surface environments. Furthermore, it is commonly proposed that surface oxygen levels played a key role in controlling the timing and tempo of the origin and early diversification of animals. Although oxygen levels were likely more dynamic than previously imagined, we make a case here that emerging records provide evidence for low atmospheric oxygen levels for the majority of Earth's history. Specifically, we review records and present a conceptual framework that suggest that background oxygen levels were below 1% of the present atmospheric level during the billon years leading up to the diversification of early animals. Evidence for low background oxygen levels through much of the Proterozoic bolsters the case that environmental conditions were a critical factor in controlling the structure of ecosystems through Earth's history.
大气氧化作用——地球历史上最根本的转变之一——极大地改变了海洋的化学成分，并提供了一个极具说服力的例子，说明生命如何能够重塑行星表面环境。此外，人们普遍认为，地表氧气水平在控制动物起源和早期多样化的时间和节奏方面发挥了关键作用。尽管氧气水平可能比之前想象的更具动态变化，但我们在此提出，新出现的记录为地球历史的大部分时间里大气氧气水平较低提供了证据。具体而言，我们回顾了相关记录并提出了一个概念框架，该框架表明，在早期动物多样化之前的数十亿年里，背景氧气水平低于当前大气水平的1%。元古宙大部分时间里背景氧气水平较低的证据支持了这样一种观点，即环境条件是控制地球历史上生态系统结构的关键因素。
