Scientists from the University of Hiroshima in Japan believe they may have solved one of science's most enduring mysteries — namely, how life sprung from non-living matter in the Earth's early development cycle, a report from New Atlas explains.
In a new paper published in the journal Nature Communications, the researchers detail how they created self-replicating protocells in the lab. They believe these lend weight to the chemical evolution hypothesis, which was first proposed in the 1920s. It states that "life first originated with the formation of macromolecules from simple small molecules, and those macromolecules formed molecular assemblies that could proliferate," Muneyuki Matsuo, first author of the study, explained in a press statement.
The Hiroshima researchers specifically set out to investigate the origin of the molecular assemblies that proliferate from small molecules, as these have remained a mystery ever since the chemical evolution scenario was first hypothesized. In the Hiroshima Univesity press statement, Matsuo calls them "the missing link between chemistry and biology in the origin of life."
Humanity's common ancestry traced back to its molecular origins
For their study, the researchers aimed to recreate these proliferating protocells in the lab. First, they created a new small molecule out of amino acid derivatives that would self-assemble into primitive cells. This was added into room temperature water at normal atmospheric pressure for observation over a period of time.
The researchers found that the molecules were arranged into peptides and then spontaneously formed droplets. By adding more amino acids, the scientists observed these droplets grow in size and then divide, a process comparable to the self-reproduction of biological cells. "By constructing peptide droplets that proliferate with feeding on novel amino acid derivatives, we have experimentally elucidated the long-standing mystery of how prebiotic ancestors were able to proliferate and survive by selectively concentrating prebiotic chemicals," Matsuo says. "Our results suggest that droplets became evolvable molecular aggregates — one of which became our common ancestor." What's more, during the experiment, some of the droplets also concentrated nucleic acids, which carries genetic information. Those droplets were also more resistant to external stimuli, the researchers said, and they were more likely to survive.
Though the findings don't conclusively tell us how life originated on the early Earth, they do lend weight to the chemical evolution hypothesis and they suggest further avenues of research for the scientific community. Scientists have also tested the RNA hypothesis, which states that RNA molecules were the first self-replicating molecules and that they eventually led to life on Earth. Other avenues of research, meanwhile, have suggested that asteroids may have brought the necessary components for life to Earth — in July, researchers from the U.S.-based Southwest Research Institute said their findings suggested that city-sized asteroids once hit Earth much more frequently than previously thought, lending weight to that particular hypothesis. Next, the Hiroshima researchers aim to continue their investigation into amino acids to gain more knowledge about how life might have started on Earth.