Unravelling life’s origin: five key breakthroughs from the past five years

By Seán Jordan, Louise Gillet de Chalonge, Dublin City University

There is still so much we don’t understand about the origin of life on Earth.

The definition of life itself is a source of debate among scientists, but most researchers agree on the fundamental ingredients of a living cell. Water, energy, and a few essential elements are the prerequisites for cells to emerge. However, the exact details of how this happens remain a mystery.

Recent research has focused on trying to recreate in the lab the chemical reactions that constitute life as we know it, in conditions plausible for early Earth (around 4 billion years ago). Experiments have grown in complexity, thanks to technological progress and a better understanding of what early Earth conditions were like.

However, far from bringing scientists together and settling the debate, the rise of experimental work has led to many contradictory theories. Some scientists think that life emerged in deep-sea hydrothermal vents, where the conditions provided the necessary energy. Others argue that hot springs on land would have provided a better setting because they are more likely to hold organic molecules from meteorites. These are just two possibilities which are being investigated.

Here are five of the most remarkable discoveries over the last five years.

Reactions in early cells

What energy source drove the chemical reactions at the origin of life? This is the mystery that a research team in Germany has sought to unravel. The team delved into the feasibility of 402 reactions known to create some of the essential components of life, such as nucleotides (a building block of DNA and RNA). They did this using some of the most common elements that could have been found on the early Earth.

These reactions, present in modern cells, are also believed to be the core metabolism of LUCA, the last universal common ancestor, a single-cell, bacterium-like organism.

For each reaction, they calculated the changes in free energy, which determines if a reaction can go forward without other external sources of energy.

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