Soluble iron began to grow scarce and competition for iron among cells increased.
According to this new theory, Earth's oceans lost most of their soluble iron because of an increase in atmospheric oxygen. When water and solid iron interact in the presence of oxygen, the iron is rapidly oxidized – which is tougher for living things to make use of.
Archaea in the thermal springs of Yellowstone, for instance, can only really thrive on iron oxide mats. Whereas modern eukaryotes can live outside of these geological sources, as long as there are biological forms of iron available.
"Despite the depletion of bioavailable iron, throughout the rebound of life post-GOE and its subsequent diversification (and passage through other successive mass extinction events), iron has retained its preeminence in biological systems," the authors write.
Given that a rise in atmospheric CO2 could increase iron deficiency in the food chain, researchers say we need to know more about how life copes with the ebbs and flows of this crucial element.
If this planet is rich enough in iron, it could indicate a possible harbor for some of the simplest forms of life