A team of researchers at The Scripps Research Institute (TSRI) have come out with a new theory for how early life on earth may have started.
Early Life On Earth
Although we have a good idea on how life continues to evolve, the origins of the first spark of life here on Earth are far more clouded. It appears as if a team of chemists may have a new take on how exactly early life on Earth may have begun.
“This was a black box for us…but if you focus on the chemistry the questions of origins of life become less daunting,” said Ramanarayanan Krishnamurthy, PhD, associate professor of chemistry at TSRI in an article published by the Scripps Institute.
Krishnamurthy and the coauthors of the study focused on discovering a series of chemical reactions that make up what we know as the citric acid cycle.
Every aerobic organism depends upon the citric acid cycle in order to release stored energy in their cells. As such, it’s a fundamental necessity for early life on earth as a process required even by the smallest of organisms. Managing to replicate this process using chemicals thought to be present during Earth’s beginnings is a key step in understanding how early life on earth came to be.
Previous forays into the study of the citric acid cycle relied on substances involved in the process today, but Krishnamurthy and his team took a different approach. Rather than focusing on the substances themselves, the team started with the chemical reactions first and then “wrote the recipe” for a modified citric acid cycle.
This new study takes two non-biological cycles – known as the HKG cycle and the malonate cycle – and outlines the possibility of how they could have combined together to launch a rudimentary version of the citric acid cycle. Both of the cycles perform the same chemistry of a-ketoacids and b-ketoacids as is used in the citric acid cycle, so it’s reasonable to assume that the combination of the HKG and malonate cycles could have given us the beginnings of this important biological process for early life on earth.
The researchers found that as these reactions were run, amino acids could be produced in addition to the CO2. The study theorizes that as these biological molecules became available, they replaced the non-biological molecules to make the process more complex and efficient. Krishnamurthy explained that “the chemistry could have stayed the same over time, it was just the nature of the molecules that changed…The molecules evolved to be more complicated over time based on what biology needed.”
Backing up this theory is the presence of glyoxylate at the center of these reactions, which was ready and waiting for early life on earth and is included in the citric acid cycle today.
More research needs to be done to understand if these reactions could have been sustainable enough to create early life on earth, but these initial findings at least suggest the possibility that non-biological cycles could have combined to form a process that is so integral to life in aerobic organisms to this day.