Unveiling LUCA: Our Ancient Common Ancestor How far back can you trace your ancestry? For many, it goes back a few gener…
Unveiling LUCA: Our Ancient Common Ancestor
How far back can you trace your ancestry? For many, it goes back a few generations, but the oldest known ancestor of all living organisms, LUCA (Last Universal Common Ancestor), lived over four billion years ago. Interestingly, LUCA is not just your ancestor but the ancestor of every living organism on Earth. Despite the passage of eons, scientists continue to learn more about him, thanks to the hundreds of genes inherited from him by all current life forms.
A recent study published in Nature Ecology & Evolution provides fascinating new insights into LUCA. Researchers compared common sequences in the genomes of 700 modern microbes from various groups. By examining the shared characteristics in the DNA of these bacteria and archaea, they estimated the time of divergence using the “molecular clock” method. This technique calculates the time of divergence between two genomes based on the number of differences between them, calibrated by fossil and isotope analysis.
The findings reveal that LUCA lived even earlier than previously thought – around 4.2 billion years ago, just as Earth was forming. Furthermore, LUCA did not live in isolation; he thrived in an ecosystem with other organisms and even possessed an immune system capable of recognizing and responding to viruses.
Remarkably, life emerged on Earth (or rather, in water) incredibly quickly! LUCA already exhibited key features of modern bacteria, being a cell with a genome encoding around 2600 proteins, comparable to present-day microbes. However, the rapid evolution of such a complex cellular apparatus remains one of science’s most intriguing mysteries.
The study also confirmed earlier findings that LUCA was an anaerobe (oxygen was toxic to him), a thermophile (thriving in heat), and derived energy from dissolved carbon dioxide and hydrogen, likely living near underwater volcanoes emitting hydrogen and heating the water.
The most groundbreaking discovery of this new research is LUCA’s immune system, which included 19 genes of the CRISPR-Cas9 apparatus. This same system, which modern bacteria use to slice the genetic material of attacking viruses, is now a revolutionary tool in genetic engineering. This method of genome editing holds immense potential, allowing us to create new organisms and control our own evolution. Yet, LUCA had CRISPR at the dawn of time, reminding us not to overestimate our technological achievements.
@science