New research from leading American institutions indicates iron stands as the oldest and sole metal that shaped the emergence of life on Earth. The study, conducted by teams at the University of Michigan, the California Institute of Technology, and the University of California at Los Angeles, appears in a long-standing, peer-reviewed scientific journal. The findings challenge prior assumptions about how early life interacted with metal elements and underscore iron’s central role in the biogeochemical environment of the ancient ocean.
According to the researchers, life depended on metals with which biological molecules could form stable interactions. In the iron-rich oceans of the distant past, iron effectively served as the primary chemical partner for early biomolecules, while other transition metals remained largely less accessible. This iron dominance would have shaped the paths available for primitive metabolic processes and the assembly of the earliest cellular systems.
Geoscientists describe the Archean Eon as a time when Earth’s oceans were vast, reducing, and heavily infused with iron. This era began roughly four billion years ago and stretched for about a billion and a half years before major atmospheric and oceanic transformations started to unfold. The ensuing Great Oxygenation Event marked a pivotal shift, introducing sustained oxygen levels that altered the chemical landscape and the balance of metals in seawater.
During this transitional period, biological systems acquired the capability to perform photosynthesis, releasing oxygen into the ancient oceans and atmosphere. Over the following hundreds of millions of years, the oceans evolved from being iron-rich and anoxic to a modern, oxygenated state. The chemical changes included the oxidation of soluble ferrous iron to ferric iron, producing insoluble iron oxides that shifted iron’s availability to living organisms and redirected the course of early biochemistry.
To explore how these changes could have affected early life, the team built a model that refreshed estimates for the concentrations of key metals, including iron, manganese, cobalt, nickel, copper, and zinc, in oceans at the time life began. By simulating how much of each metal could have been present, the researchers examined which metals early biomolecules could coordinate with and how these interactions would influence the emergence of metabolic pathways.
Findings suggest that simple biomolecules favored binding to iron, guiding the chemical routes available to primitive organisms. When iron shifted from a bioavailable to a less accessible form as oxidation progressed, ancient life forms would have needed to adapt. This reorientation could have driven diversification, enabling a spectrum of biological strategies that ultimately contributed to the rich tapestry of life on Earth.
These insights add a new dimension to the longstanding questions about how the first cells arose. By focusing on the metal chemistry of the early oceans and the way it steered molecular interactions, the research paints a clearer picture of the environmental constraints that shaped early biology and the subsequent evolution of life on our planet.