All Life on Earth Shares an Ancestor – And Some of Our Genes Predate It : ScienceAlert

Title: Ancient Genes Predating LUCA Hint at Life’s Mysterious Origins

In a groundbreaking revelation that could reshape our understanding of life’s beginnings, scientists have uncovered evidence suggesting that some of the fundamental genes in all living organisms today may have originated before the last universal common ancestor (LUCA), the most ancient life form we can study through evolutionary methods.

A team of biologists, including Aaron Goldman of Oberlin College, Greg Fournier of MIT, and Betül Kaçar of the University of Wisconsin-Madison, has published a new perspective in Cell Genomics that highlights the importance of “universal paralogs”—rare, ancient gene families found across every branch of life on Earth. These gene families, which duplicated before the major branches of life split apart, offer a tantalizing glimpse into the genetic toolkit of life forms that predate LUCA itself.

The Roots of Life’s Family Tree

LUCA, which lived roughly 4.2 billion years ago, is often considered the trunk of the genetic family tree. But what about the roots? The researchers argue that the existence of universal paralogs points to earlier, single-celled organisms that harbored these duplicate genes—long-buried precursors that helped give rise to animals, plants, fungi, and bacteria.

“These universal paralogs are our only window into the earliest cellular lineages,” explains Fournier. “They provide us with a chance to transform the deepest unknowns of evolution and biology into discoveries we can actually test.”

A Complex Evolutionary Process

The study suggests that the transition to a modern genetic code before LUCA was not a simple, linear process. Instead, it was a complex evolutionary journey involving multiple mechanisms, including co-evolution with amino acid biosynthesis pathways. For example, recent research has revealed that enzymes called aminoacyl tRNA synthetases, which are crucial for tying the right amino acid to its matching transfer RNA, have ancestors that predate LUCA. This implies that early life forms could already incorporate amino acids into genetically encoded proteins before their more modern relatives evolved.

The Challenge of Ancient Genes

Despite the significance of these findings, the researchers caution that the number of known universal paralog protein families is still limited. Over time, many paralogs in the LUCA proteome were likely lost due to evolutionary events, genetic divergence, or horizontal gene transfer—a common way bacteria share genes across populations. This makes the study of these ancient genes both challenging and incredibly valuable.

A New Frontier in Evolutionary Biology

As scientists continue to refine ancestral sequence reconstructions, the study of universal paralogs could unlock new insights into the origins of life on Earth. “By following universal paralogs, we can connect the earliest steps of life on Earth to the tools of modern science,” says Kaçar. “This is a chance to explore the deepest unknowns of evolution and biology.”

The implications of this research are profound. If some of the genes in LUCA’s genome are much older than the organism itself, it suggests that life’s genetic toolkit was already sophisticated and diverse long before LUCA emerged. This challenges the notion that life began with a single, simple ancestor and instead points to a more complex and interconnected evolutionary history.

Conclusion

The discovery of ancient genes predating LUCA is a reminder of how much we still have to learn about the origins of life on Earth. As scientists continue to probe the depths of evolutionary history, universal paralogs may hold the key to unlocking some of biology’s most enduring mysteries. This research not only deepens our understanding of life’s beginnings but also highlights the incredible resilience and adaptability of life itself.

Tags: #AncientGenes #LUCA #OriginsOfLife #EvolutionaryBiology #Genetics #UniversalParalogs #CellGenomics #Science #Biology #LifeOnEarth

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