The origin of life on Earth poses a basic paradox: basic biochemicals like nucleotides and catalysts like proteins need each other to exist, but one must have come first. We may now have an answer, thanks to the transition metals.
In order to build complex catalysts like proteins or ribozymes, you first need biochemicals, which - and here's the tricky part - can only exist if there are catalysts around to direct their formation. It's the classic chicken-and-the-egg paradox, and nothing less than the existence of all life on this planet is at stake.
A team of researchers may have found a way round this rather dizzying paradox by identifying a different group of catalysts that could theoretically create life. Their theory holds that transition metal elements, such as iron, copper, and nickel, could have combined with tiny organic molecules known as ligands. The structures they formed would then catalyze the creation of biochemicals, which would then be able to develop the more complex biological catalysts we see today.
Harold Morowitz of George Mason University says this explanation reveals just how complex the origins of life really are:
"We used to think if we could understand what carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur were doing, we would immediately be able to understand biology. But now we're finding that these other fairly rare elements, transition metals, are necessary in biology, so we ask, 'What was their role in the origin of life?' The idea has emerged from a study of the periodic table. We strongly feel that unless you're able to see how life comes about in some formal chemical way, you're never really going to solve the problem."
The scientists believe these metal-ligand structures clumped together in ancient hydrothermal ocean vents, undergoing a series of chemical reactions that created increasingly complex molecules. It's from there that the first molecules of life emerged. Their theory views life as little more than a necessary byproduct of the interaction between transition metals and ligands, which means their ideas should be theoretically testable.
It also means, as Morowitz explains, that life could easily have arisen more than once on Earth, and it might place some fundamental constraints on what life can look like elsewhere:
"Life could have originated multiples times, and, if we find life elsewhere in the universe, it could be very similar to the life we know here because it will be based on the same transition metals and ligands. It's a conjecture at the moment, but it could become a formal scientific core for the emergence of life."