When did life on Earth really begin?

The first living things on our planet appeared 100 million years earlier than previously thought, according to a new study.

About 3.9 billion years ago – shortly after Earth was hit by the planet Theia and while it was still facing a flurry of meteors – the ancestors of all living things were born.

Scientists have traditionally used the fossil record to trace the origin of life on Earth, but the further into the past, the more difficult it is to find this result.

Dr Holly Betts at the University of Bristol, lead author of the study, explains: “The problem with the first fossil record of living things is that it is very limited and difficult to interpret – careful reanalysis of some the oldest fossils have shown they are crystals, not fossils.”

When did life on Earth really begin?
Life on Earth cannot be longer than 4.5 billion years.

In the study, published in the journal Nature Ecology and Evolution, Betts and her colleagues used a combination of fossil and genetic data to find the so-called “Luca” – a common ancestor. final variable.

“The fossils do not represent the only line of evidence for understanding the past,” said co-author Professor Philip Donoghue.

“The second record of life has survived, preserved in the genomes of all living things.”

By combining data from all available sources, scientists can build “molecular clocks” , based on the idea that the number of genetic code differences between different species is proportional. with 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 of the emergence of all major groups of organisms such as bacteria.

The scientists concluded that the hypothetical Luca existed before the period of “heavy bombardment” when many meteorites hit the Earth.

This is earlier than the oldest fossil evidence of life – evidence no more than 3.8 billion years old.

While there are still uncertainties, scientists know that life on Earth cannot last longer than 4.5 billion years, when Theia crashed into the fledgling planet.

This devastating event not only devastated the Earth but eventually helped create the Moon, which had the effect of wiping out the planet and killing any life that had existed there.

Since early life consisted of tiny microscopic cells, surviving fossils are rarely found, and they are the source of much debate.

Some have suggested the carbon found in a 4.1 billion-year-old mineral called zircon could be evidence of ancient life, but this has yet to be confirmed.