More than three billion years ago, life on Earth faced a difficult problem.
The planet’s oceans contained only tiny amounts of molybdenum, a rare metal that modern life depends on today.
Yet new research shows that some of the earliest living organisms were already using this metal long before it became common in the environment.
The discovery changes scientists’ understanding of how early life evolved and survived on the young Earth.
The study, published in Nature Communications, suggests that life found ways to use molybdenum much earlier than researchers once believed.
Molybdenum may sound unfamiliar, but it plays an important role inside living cells. It helps certain enzymes carry out essential chemical reactions linked to carbon, nitrogen, and sulfur.
These reactions are necessary for life because they support processes such as energy production and the movement of nutrients through ecosystems.
Without molybdenum, many of these reactions would happen far too slowly to support life.
According to Betül Kaçar, senior author of the study and leader of the Kaçar Lab at the University of Wisconsin–Madison, understanding when life first began using molybdenum helps scientists understand when some of Earth’s earliest metabolic systems became possible.
Today, molybdenum is relatively common. But billions of years ago, during the Archean Eon, Earth’s oceans contained only trace amounts of it.
Scientists previously thought early life may have relied instead on another metal called tungsten, which behaves in similar ways inside cells and is still used today by some microbes living in extreme environments.
This led to a popular idea among researchers known as the “tungsten first” theory. According to this theory, ancient organisms first evolved using tungsten and only switched to molybdenum later, after oxygen levels rose and molybdenum became easier to find.
The new study challenges that idea.
The research team examined geological records and reconstructed the history of metal use across the tree of life. Their findings suggest that both molybdenum and tungsten were already being used by ancient microbes between about 3.7 and 3.1 billion years ago. This was long before the Great Oxidation Event, a major turning point around 2.45 billion years ago when oxygen levels in Earth’s atmosphere began to rise dramatically because of photosynthetic microorganisms.
The researchers believe early life may have found small pockets of molybdenum in special environments deep beneath the oceans. Hydrothermal vents on the seafloor release many metals into the surrounding water, including iron, copper, nickel, cobalt, tungsten, and molybdenum. These underwater volcanic systems may have acted as safe havens where early microbes could access the rare materials they needed.
Even though molybdenum was scarce, it may have offered important advantages. The metal is highly effective at helping enzymes work under many different chemical conditions, which could explain why life evolved ways to find and use it despite its rarity.
The findings may also help scientists searching for life beyond Earth. Researchers say the study reminds us that alien life may not follow the same rules or chemical pathways seen on modern Earth today.
Instead of searching only for planets that look exactly like Earth, scientists may need to think more broadly about how life could adapt to very different environments with different metals, chemistry, and oxygen levels.
The study suggests that life can be surprisingly creative when it comes to surviving under harsh conditions.
