The first living thing to emerge on our planet appeared at least 100 million years earlier than previously thought, according to a new study.
Around 3.9 billion years ago – shortly after the Earth had been struck by the planet Theia and while it still faced a barrage of meteors – the ancestor of all living things sprang into being.
Scientists have traditionally used the fossil record to trace the origins of life on Earth, but the further back in the planet’s history they travel the more difficult this becomes.
By combining data from all available sources scientists are able to construct “molecular clocks”, based on the idea that the number of differences in genetic code between different species is proportional to the time since they shared a common ancestor.
Using information on 29 genes from a total of 102 living organisms, the team assembled a timeline with dates for the appearance of all the major groups of life forms, such as bacteria.
The scientists concluded that the hypothetical Luca existed before the “late heavy bombardment” when multiple meteors smashed into Earth.
This is far earlier than the oldest fossil evidence of life, which is no more than 3.8 billion years old.
Source link: https://www.independent.co.uk/news/science/first-life-earth-theia-luca-meteor-fossils-molecular-clocks-a8501226.html
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