Modern life requires many different metal ions, which enable diverse biochemical functions. It is commonly assumed that metal ions’ environmental availabilities controlled the evolution of early life. We argue that evolution can only explore the chemistry that life encounters, and fortuitous chemical interactions between metal ions and biological compounds can only be selected for if they first occur sufficiently frequently. We calculated maximal transition metal ion concentrations in the ancient ocean, determining that the amounts of biologically important transition metal ions were orders of magnitude lower than ferrous iron. Under such conditions, primitive bioligands would predominantly interact with Fe(II). While interactions with other metals in certain environments may have provided evolutionary opportunities, the biochemical capacities of Fe(II), Fe–S clusters, or the plentiful magnesium and calcium could have satisfied all functions needed by early life. Primitive organisms could have used Fe(II) exclusively for their transition metal ion requirements.

中文翻译：

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铁：生命的原始过渡金属


现代生命需要许多不同的金属离子，从而实现不同的生化功能。人们普遍认为金属离子的环境可用性控制着早期生命的进化。我们认为，进化只能探索生命遇到的化学反应，而金属离子和生物化合物之间的偶然化学相互作用只有在它们首先足够频繁地发生时才能被选择。我们计算了古代海洋中的最大过渡金属离子浓度，确定具有生物学重要意义的过渡金属离子的含量比二价铁低几个数量级。在这种条件下，原始生物配体主要与 Fe(II) 相互作用。虽然在某些环境中与其他金属的相互作用可能提供了进化机会，但 Fe(II)、Fe-S 簇或丰富的镁和钙的生化能力可以满足早期生命所需的所有功能。原始生物可能专门使用 Fe(II) 来满足其过渡金属离子的需求。