A debate is brewing in the scientific world that could overturn fundamental concepts regarding the origin of life on Earth. A group of researchers from Heinrich Heine University in Düsseldorf (Germany) has published a paper in the prestigious journal Science Advances that challenges the dogma of a single universal common ancestor for all living organisms. According to new data, the transition from non-living chemical matter to fully functional living cells may have occurred on our planet twice, independently of each other.
The End of the LUCA Era: Two Paths to Autonomy
For a long time, the scientific community has operated on the concept of LUCA (Last Universal Common Ancestor). It was believed that all existing forms of life today, from bacteria to humans, trace their origins to a single cell that emerged billions of years ago. However, a new analysis of enzymes and basic chemical reactions has revealed significant differences between the two main branches of prokaryotes — bacteria and archaea.
Study leader William Martin and his colleagues discovered that the enzymes responsible for catalyzing the same basic metabolic reactions have fundamentally different structures in these two groups. This suggests that bacteria and archaea formed their own autonomous metabolic systems separately from one another. It turns out that LUCA was not a fully fledged living organism in the modern sense, but rather a set of genetic code and primitive mechanisms that subsequently evolved along two different trajectories.
The Role of Metals and Hydrothermal Vents
Scientists hypothesize that the first chemical reactions that became the foundation for life took place in extreme conditions near underwater hydrothermal vents. In the early stages of evolution, the role of catalysts was performed not by protein enzymes, but by natural metals, such as palladium, present in the water. It was these metals that facilitated the conversion of hydrogen, ammonia, and carbon dioxide into organic molecules.
A key discovery was the resolution of the long-standing problem of the energy source for primary metabolism. Modern cells use the molecule ATP for this, the synthesis of which itself requires complex enzymatic processes. Experiments showed that in the early stages, this role could have been performed by phosphite — a form of phosphorus naturally found at hydrothermal vents and easily entering reactions without the involvement of enzymes. This allowed primitive systems to function before the emergence of complex protein structures.
Parallel Evolution: From Chemistry to Biology
According to the new hypothesis, bacteria and archaea independently developed their own protein enzymes to replace inorganic metal catalysts and become fully autonomous cells. This phenomenon can be characterized as parallel evolution: humanity observes a single origin of the genetic code, but two separate sources of full-fledged cellular life.
If the scientists' conclusions are confirmed by further research, the traditional "tree of life" will have to be radically rewritten. Instead of a single common trunk from which all branches of the biosphere diverge, it may have two separate roots, formed even before the appearance of the first fully functional cells. This opens new horizons for the search for life on other planets, where conditions may facilitate the emergence of biochemistry different from that of Earth.
