- In a new peer-reviewed analysis, scientists quantify amino acids before and after our “last universal common ancestor.”
- The last universal common ancestor is the single life form that has spread since then.
- The Earth of four billion years ago could help us detect the presence of life on one of Saturn’s moons today.
Scientists argue for adjusting our understanding of how Genoa appeared for the first time. For some time, there has been consensus on the order in which the constituent amino acids were “added” to the box of Lego pieces that build our genes. But according to genetic researchers at the University of Arizona, our previous assumptions may reflect biases in our understanding of biotic (living) versus abiotic (non-living) sources.
In other words, our current working model of gene history might underestimate the beginnings of protolife (which included precursors like RNA and peptides) compared to what appeared with and after the start of life. Our understanding of these extremely ancient times will always be incomplete, but it is important for us to continue to study the early Earth. Scientists say any improvement in this understanding could not only allow us to learn more about our own history, but also help us search for the beginnings of life elsewhere in the universe.
In this new article, published in peer-reviewed journal Proceedings of the National Academy of SciencesResearchers led by lead author Joanna Masel and first author Sawsan Wehbi explain that vital elements of our proteins (aka amino acids) date back four billion years, to the last universal common ancestor (LUCA) of all life on Earth. These chains of dozens or more amino acids, called protein domains, are “like a wheel” on a car, Wehbi said in a statement: “It’s a part that can be used in many different cars, and wheels have been around much longer than cars.”
The group used specialized software and data from the National Center for Biotechnology Information to create an evolving tree (so to speak) of these elements. protein areas that were only theorized or observed in the 1970s. Our knowledge of these details has grown by leaps and bounds.
A big paradigm shift proposed by this research is the idea that we should rethink the order in which the 20 essential genetic factors amino acids emerged from the stew of primeval Earth. Scientists argue that the current model overestimates how often an amino acid appears early in life, leading to a theory that the amino acid found in the highest saturation must have emerged first. This fits with existing research, such as a 2017 paper suggesting that our amino acids represent the best of the bestnot just a “frozen accident” of circumstances. In the new paper, scientists say the amino acids could even come from different parts of the young Earth, rather than all from a uniform environment.
Tryptophan, the maligned “sleepy” amino acid found in Thanksgiving Turkeywas particularly notable for scientists (its letter is W). “There is scientific consensus that W was the last of the 20 canonical amino acids to be added to the genetic code,” the scientists wrote. But they found 1.2% W in the pre-LUCA data and only 0.9% post-LUCA. These values may seem small, but it represents a difference of 25%.
Why would the last amino acid to emerge be more common before the resulting ramification of all life? The team hypothesized that the chemical explanation could point to an even older version of the genetics idea. As in all things evolutionarythere is no intuitive reason why a successful thing must be the only one of its kind or family to exist.
“The stepwise construction of the current code and the competition between ancient codes could have occurred simultaneously,” the scientists conclude. And, tantalizingly, “ancient codes could also have used non-canonical amino acids.” These may have emerged around alkaline hydrothermal vents, thought to play a key role in the emergence of life, despite the fact that the resulting phenomena life forms didn’t live there long.
To apply this theory to the rest universewe don’t need to go far either. “A biotic synthesis of aromatic amino acids could be possible in the water-rock interface of the underground ocean of Enceladus,” explain the scientists. It’s only up to Saturn. Maybe a solar system block party is closer than we think.
Caroline Delbert is a writer, avid reader and editor-in-chief at Pop Mech. She’s also passionate about just about everything. His favorite subjects include nuclear energy, cosmology, everyday mathematics, and the philosophy of it all.