A New Clue To How Life First Emerged On Earth

This year the fascinating subject of how life began on our planet has seen me add several postings. In May, I wrote about a hypothesis linking changes in the Earth’s magnetic field to triggering the emergence of life. In October, I described a theory that linked gas flows over narrow channels of water in the early ocean creating suitable environments for nucleic acids to form and replicate. Last month, I described the theory of chirality being responsible for producing left-handed amino acids and right-handed sugars that could bond together and form nucleic acids leading to the emergence of RNA and eventually DNA. All or none of these hypotheses could explain how life emerged the way it did here on Earth.

Now, new research from the University of California San Diego (UCSD) looks at the emergence of self-contained lipid membranes or vesicles made from long chains of fatty acids that could have formed the architecture for the first living cells to emerge.

The research appears in an article on October 30, 2024, in the journal Nature Chemistry and is described in a UCSD press release issued on November 13, 2024. Not all fatty acids are the same. The research points to the amino acid cysteine in reaction with thioesters producing diacyl lipids that formed protocell-like membranes. Silica acts as a catalyst in the presence of this chemistry and its abundance would have ensured the building blocks were in place for the evolution of the first living cell.

Neal Deveraj is a Professor of Chemistry and Biochemistry at UCSD. He admits that lipid production commonly occurs in the presence of enzymes today, but “over four billion years ago, there were no enzymes. Yet somehow these first protocell structures were formed.” How could this happen? Deveraj and his time theorize that a catalyst material could have been the reactive agent causing self-contained lipid vesicles to form containing a variety of biochemical content. They chose silica glass as a likely catalyst candidate.

Two fatty acids, cysteine and thioesters, in low concentrations and in the presence of silica glass showed how protocell-like membranes “stable enough to sustain biochemical reactions” could self-generate.

Deveraj notes that this doesn’t definitively prove how life emerged, but in the absence of life, provides a plausible “matter-to-life transition” mechanism because silica would have been widely present in the oceans of early Earth.

What is so important about lipids? Lipids are fatty compounds that today absorb vitamins, store energy and form the structural components of living cell membranes. The catalytic reaction of two chemicals in the presence of silica glass, in this case, cysteine and thioesters, produces lipid membrane vesicles containing a chemical brew within them. This would have been a necessary first step to move from a prebiotic Earth of 4 billion years ago to one where living cells capable of replicating could emerge.

For a demonstration of just how the process would have worked, watch the spontaneous emergence of self-contained lipid membranes in this time-lapse fluorescence microscopy video, recorded by Deveraj’s researchers, showing lipid vesicles forming. The images were taken every 2 minutes over 4 hours.