Iron is an irreplaceable component of proteins and enzyme systems required for life. This need for iron is a well-characterized evolutionary mechanism for genetic selection. However, there is limited consideration of how iron bioavailability, initially determined by planetary accretion but fluctuating considerably at global scale over geological time frames, has shaped the biosphere. We describe influences of iron on planetary habitability from formation events >4 Gya and initiation of biochemistry from geochemistry through oxygenation of the atmosphere to current host–pathogen dynamics. By determining the iron and transition element distribution within the terrestrial planets, planetary core formation is a constraint on both the crustal composition and the longevity of surface water, hence a planet’s habitability. As such, stellar compositions, combined with metallic core-mass fraction, may be an observable characteristic of exoplanets that relates to their ability to support life. On Earth, the stepwise rise of atmospheric oxygen effectively removed gigatons of soluble ferrous iron from habitats, generating evolutionary pressures. Phagocytic, infectious, and symbiotic behaviors, dating from around the Great Oxygenation Event, refocused iron acquisition onto biotic sources, while eukaryotic multicellularity allows iron recycling within an organism. These developments allow life to more efficiently utilize a scarce but vital nutrient. Initiation of terrestrial life benefitted from the biochemical properties of abundant mantle/crustal iron, but the subsequent loss of iron bioavailability may have been an equally important driver of compensatory diversity. This latter concept may have relevance for the predicted future increase in iron deficiency across the food chain caused by elevated atmospheric CO₂.

铁是生命所需的蛋白质和酶系统中不可替代的成分。这种对铁的需求是遗传选择的一个充分表征的进化机制。然而，对于铁的生物利用度（最初由行星吸积决定但在地质时间框架内在全球范围内大幅波动）如何塑造生物圈的考虑有限。我们描述了铁对行星宜居性的影响，从形成事件> 4 Gya和从地球化学到大气氧合到当前宿主-病原体动力学的生物化学启动。通过确定类地行星内铁和过渡元素的分布，行星核心的形成是对地壳成分和地表水寿命的限制，因此是行星的可居住性。因此，恒星组合物，结合金属核心质量分数，可能是系外行星的一个可观测特征，与它们维持生命的能力有关。在地球上，大气中氧气的逐步上升有效地从栖息地中去除了数十亿吨的可溶性亚铁，从而产生了进化压力。吞噬、传染和共生行为，可追溯到大氧合事件前后，将铁的获取重新集中在生物来源上，而真核多细胞性则允许铁在生物体内循环。这些发展使生命能够更有效地利用稀缺但重要的营养素。陆地生命的起源得益于丰富的地幔/地壳铁的生化特性，但随后铁生物利用度的丧失可能是补偿多样性的一个同样重要的驱动因素。₂ .