UNITED STATES (OBSERVATORY) – A new study found that the first forms of life appeared on our planet, before what we thought was at least 100 million years ago.
About 3.9 billion years ago, shortly after the Theia collided with the Earth, which was subject to a shower of meteors at that time, the first ancestor appeared to all living beings.
Traditionally, scientists have used the fossil record to trace the origins of life on earth, but the more they go back in the history of the planet, the harder and more complex the study becomes.
“The problem of the early fossil record of life is very limited and difficult to explain. The careful reinterpretation of some ancient fossils has shown that they are crystals, not fossils at all,” said doctoral student Holly Bates, the lead author of the study from the University of Bristol.
In a study published in the journal Nature Ecology and Evolution, Bates and her colleagues used a set of fossil and genetic data to track the so-called Luca, the last common global ancestor.
“Fossils do not represent the only guide to understanding the past, where there is another record of life, preserved in the genes of all living things,” said co-author Professor Philip Donahue.
By combining data from all available sources, scientists can build “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 out of a total of 102 living organisms, scientists have compiled a timeline with the dates of appearance of all major groups of life forms, such as bacteria.
The scientists concluded that the “Luca” default was present before the “heavy bombing late”, when multiple meteorites crashed on the ground. This date precedes the oldest fossil record of life, which is only 3.8 billion years old.
While there are still doubts, scientists have found that life on Earth can not extend beyond 4.5 billion years, when Theia collided with the newborn planet.
It should be noted that this event did not lead to the scattering of pieces of land, formed the moon in the end, but contributed to “sterilize” the planet and kill any life that already exists on its surface.
Since the first life consists of small microscopic cells, the remaining fossils are rarely found, especially those that have been the source of much controversy.