Every living organism uses tiny quantities of metals to carry out biological functions, including breathing, transcribing DNA, turning food into energy, or any number of essential life processes. Life has used metals in this way since single-celled organisms floated in Earth’s earliest oceans. Nearly half of the enzymes—proteins that carry out chemical reactions in cells—within organisms require metals, many of which are transition metals named for the space they occupy in the periodic table.
Now, Jena Johnson, along with scientists from Caltech and UCLA, argue that iron was life’s earliest, and sole, transition metal.
“We make a radical proposal: Iron was life’s original and only transition metal,” said Johnson. “We argue that life only relied on metals that it could interact with, and the iron-rich early ocean would make other transition metals essentially invisible.”
Their study is published in the Proceedings of the National Academy of Sciences.