Scientists Are Pretty Close to Replicating the First Thing That Ever Lived

Where did we all come from? It's a question that has lit fires of curiosity in philosophers, theologians, and more recently (at least, historically speaking) scientists for millennia. While the the older guard of high thought used stories or metaphors to derive life's origin story, scientists instead learn about the inner workings of life's smallest building blocks in an attempt to understand how they first formed life billions of years ago.

This long scientific exploration has led most evolutionary biologists to the conclusion that, for at least 400 million years, Earth was an "RNA World." The hypothesis suggests that life first took form due to self-replicating RNA, before the evolutionary arrival of DNA or even proteins.

But there's a couple problems.

First, there's no trace of this "first replicator" in known biology. And second, scientists have failed to convincingly replicate RNA in an environment similar to early Earth. While scientists are very much still on the hunt for evidence that validates the first of these two issues, a team from University College of London (UCL) is closing in on solving the second problem.

Published in the journal Nature Chemistry, a team of UCL scientists (along with experts from the MRC Laboratory of Molecular Biology in Cambridge) used three-letter "triplet" RNA building blocks subjected to acid and heat in water. This separated the RNA double-helix—the structure that makes replication so difficult—and scientists froze the solution.

What occurred next is possibly an intimate glimpse of how life first formed on Earth—between the liquid gaps of the ice crystals, these building blocks coated the RNA strands and prevented them from zipping back together. After the scientists thawed the solution and and made adjustments to pH and temperature, the RNA replicated again and again. Eventually, the strand was so long that these structures could perform biological functions.

"The triplet or three-letter building blocks of RNA we used, called trinucleotides, do not occur in biology today, but they allow for much easier replication. The earliest forms of life are likely to have been quite different from any life that we know about," James Attwater, lead author of the study from UCL, said in a press statement. "The changing conditions we engineered can occur naturally, for instance with night and day cycles of temperature, or in geothermal environments where hot rocks meet a cold atmosphere."

UCL has long been involved in constructing the play-by-play of life's origins on Earth. In 2017, for example, a study analyzed the chemistry that provided Earth with the very nucleotides necessary to construct the first RNA structures. This new study now attempts to understand, in a lab setting, how those ancient RNA first began replication, a process that's essential to understanding the foundation of life.

"Life is separated from pure chemistry by information, a molecular memory encoded in the genetic material that is transmitted from one generation to the next," Philipp Holliger, the senior author of the study from MRC Laboratory of Molecular Biology, said in a press statement. "For this process to occur, the information must be copied, i.e. replicated, to be passed on."

Currently, the researchers have only been able to replicate roughly 17 percent of the RNA strand (roughly 30 out of 180 letters), but the team says there's no reason they won't achieve complete replication with improved enzyme efficiency. The researchers also note that this reaction can't occur in saltwater (the salt disrupts the freezing process), but geothermal freshwater lakes or ponds would be the perfect chemical setting for RNA replication to take hold.

Although many questions remain, Earth's ancient RNA World could have actually had the capacity for self-replication. It's an intriguing step forward, but the scientific journey continues.