A flask of Houston’s rain helped answer a long-running question about the origin of cellular life.

The solution is proposed by two University of Houston scientists, William A. Brookshire Department of Chemical Engineering (UH ChBE) former grad student Aman Agrawal (now a postdoctoral researcher at University of Chicago’s Pritzker School of Molecular Engineering) and Alamgir Karim, UH Dow Chair and Welch Foundation Professor of chemical and biomolecular engineering, and director of both the International Polymer & Soft Matter Center and the Materials Engineering Program at UH. They were joined by UChicago PME Dean Emeritus Matthew Tirrell and Nobel Prize-winning biologist Jack Szostak in an article published last week in Scientific Advances.

For two decades, scientists like Szostak have hypothesized that RNA fragments were the first components of life to form in the Earth’s primordial seas 3.8 million years ago. Although DNA is an essential component of cellular life, it can’t fold proteins, making it unlikely to be the initial starting point. Since RNA can fold proteins, it could have been the catalyst for cellular growth and evolution.

The problem is that seawater molecules allow RNA to bond and change too quickly, often within minutes. Rapid dissipation means no segregation of material, and thus no evolution. Szostak himself proved in 2014 that regular seawater doesn’t allow RNA fragments to form the membranes necessary for cellular life.

Then along comes Agrawal. He wasn’t looking into the origin of life. He was an engineer studying the properties of complex liquids for his doctorate. Karim was his thesis adviser and introduced Agrawal to Tirrell, who brought up the RNA problem over a lunch and some theories about how if the water was distilled it may have solved it. Where would you get distilled water 3.8 billion years ago?

“I spontaneously said ‘rainwater!’” says Karim. “His eyes lit up and he was very excited at the suggestion,” Karim said. “So, you can say it was a spontaneous combustion of ideas or ideation!”

Using RNA samples from Szostak, they saw that distilled water increased the differences in exchange rate between samples from minutes to days, long enough for the RNA to begin mutation.

Distilled lab water is nothing like prehistoric rain, though. Luckily, a typical Houston downpour occurred during the research. Agrawal and fellow UH graduate student, Anusha Vonteddu ran outside with beakers to collect some. The samples again formed meshy walls, separating the RNA and possibly showing how life began from these fragments billions of years ago.

“The molecules we used to build these protocells are just models until more suitable molecules can be found as substitutes,” Agrawal said. “While the chemistry would be a little bit different, the physics will remain the same.”