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A new study is challenging long-held beliefs about the origins of life and the building blocks that led to the first genes.
For years, scientists believed there was a clear order in which amino acids (the building blocks of proteins) came together to form life. But now, researchers at the University of Arizona suggest that our understanding could be wrong, and the story of life's origins is more complex.
The study argues that we've focused too much on the amino acids that appeared after life began and not enough on the molecules that came before, such as RNA and peptides.
These might have played a key role in the transition from non-living chemistry to life. Understanding these early stages could not only change our view of life on Earth but also help us search for life elsewhere in the universe.
Published in the Proceedings of the National Academy of Sciences, researchers explain how amino acids date back four billion years.
Lead author Sawsan Wehbi used an analogy to explain how these domains were likely shared by many early life forms: "It’s a part that can be used in many different cars, and wheels have been around much longer than cars."
In other words, these amino acid chains were not specific to any one organism but were common in the earliest forms of life.
Through advanced software and data from the National Center for Biotechnology Information, researchers were able to map out how these protein domains evolved over time.
Their major finding is that the order in which the 20 essential amino acids appeared may not have been as straightforward as we thought.
Previous arguments suggested that the amino acids most abundant in early life must have been the first to emerge. However, the latest findings suggest that amino acids could have come from different regions of early Earth and that their abundance doesn’t necessarily determine their order in the genetic code.
One example is tryptophan, the amino acid that is typically considered the last to be added to the genetic code.
The study found that tryptophan was more common in early life forms, meaning that the evolution of life might have been more complicated than a simple, step-by-step process.
Researchers also proposed that early life may have used different genetic "codes" simultaneously. Some of these may have relied on non-standard amino acids, possibly formed in environments like alkaline hydrothermal vents, which are thought to be key to life's origins.
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