Triops Longicaudatus
Triops Longicaudatus Red
Triops Longicaudatus
Triops Longicaudatus Red
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Luca: First ancestor of all living beings could have existed 4.2 billion years ago
Today’s living creatures have many things in common, including the use of the same genetic code. Biologists therefore suspect that all living beings today have a common hypothetical ancestor, called Luca, which stands for ‘Last Universal Common Ancestor’. This last common ancestor of all known life forms could have lived much earlier than previously assumed, namely around 4.2 billion years ago.
Only about 400 million years younger than the solar system
Until now, it was assumed that Luca was at most 3.9 billion years old, as early life would probably not have survived the so-called late heavy bombardment, in which numerous celestial bodies hit the Earth around 4 billion years ago. However, recent studies suggest that these impacts may have been less violent than previously thought. This would mean that the last common ancestor could have lived much earlier. This is the conclusion of a study published in the journal ‘Nature Ecology & Evolution’. An international research team traced the family tree of the species back to their presumed beginnings: according to the study, it is a single-celled organism that resembles modern bacteria. However, other organisms and viruses could also have existed at that time, the researchers write.
The team assumes that Luca’s genome consisted of around 2.75 million base pairs – a comparable order of magnitude to today’s prokaryotes, i.e. single-celled organisms without a cell nucleus. ‘But what is really interesting is that he obviously had an early immune system,’ says co-author Davide Pisani from Bristol. ‘This shows that our ancestor was already in an arms race with viruses 4.2 billion years ago.’ If the study’s calculations are correct, Luca would only be around 400 million years younger than the solar system. However, the results fit in with current views on the habitability of the early Earth.
Luca’s presumed genome already contained genes for a simple Crispr system, a precursor to the Crispr-Cas system used by modern bacteria to defend themselves against viruses and used as gene scissors in biotechnology. ‘Our work combines data and methods from several disciplines and leads to insights about the early Earth and life that no single discipline could develop alone,’ says Philip Donoghue from the University of Bristol, co-author of the study. The results also show that an ecosystem was probably already established at the time of Luca.
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