Life on Earth formed after huge planet, Theia, smashed into our world

Rob Waugh
“Fossils can only tell us so much.” (Getty)

Billions of years ago, a mysterious planet called Theia smashed into Earth, knocking off a hunk of debris that would form the moon.

In the wake of this terrifying cataclysm, the first seeds of life on Earth flourished, University of Bristol researchers claim.

The rsearchers analysed DNA to trace back the ancestor of all living things – and concluded that the ‘Last Universal Common Ancestor’, the grandfather of all life forms, lived 100 million years earlier than thought.

Professor Davide Pisani said: ‘Using this approach we were able to show that the Last Universal Common Ancestor of all cellular life forms, ‘LUCA’, existed very early in Earth’s history, almost 4.5 Billion years ago – not long after Earth was impacted by the planet Theia, the event which sterilised Earth and led to the formation of the Moon.

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‘This is significantly earlier than the currently accepted oldest fossil evidence would suggest.’


Using DNA to ‘trace’ the ancestry of life on Earth allows the researchers to go ‘further back’ in time than approaches using fossils, the researchers say.

Holly Betts, lead author of the study, from the University of Bristol’s School of Earth Sciences, said: ‘There are few fossils from the Archaean and they generally cannot be unambiguously assigned to the lineages we are familiar with, like the blue-green algae or the salt-loving archaebacteria that colours salt-marshes pink all around the world.