Going back in genes

A new analysis of the genes common to bacteria and archaea offers strong evidence that the earliest cells on Earth lived deep in hydrothermal vents, explains William F Martin

The Biologist 64(2) p20-23

The last universal common ancestor (LUCA) is the name given to the most recent common ancestor of all existing life on Earth. It is the population of cells from roughly four billion years ago from which all life found on Earth today evolved.

We know LUCA must have had a DNA-based genetic code, because all descendant life forms do. But how did LUCA harness energy? The chemical reactions that help cells harness energy from their environments today seem almost as diverse as life itself.

We looked at that question using data from sequenced microbial genomes[1]. We concluded that LUCA probably lived from gases – H2, CO2, CO, N2 – in a setting that looked very much like a modern submarine hydrothermal vent.

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