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Self-Replicating Droplets: Evidence or a Shot in the Dark?

Sarah Chaffee


When scientists judge explanations for the origin of life that employ strictly chemical means, the evidentiary bar often seems notably low. For example, consider a new article on the Chemistry World website, published by the Royal Society of Chemistry. It claims, “Key riddle of life’s origin may be answered by primitive protocells that can divide,” and references a study in Nature Physics.

Generally, chemical evolution theorists assume that three components must have been necessary for the first living cell: 1) metabolism, 2) RNA/DNA, and 3) a containment structure or primitive cell wall to separate the first two components from the outside world. This study aims to address the third issue.

Researchers found that droplets, when influenced by an energy source, grow by absorbing moisture from their surroundings and then divide when they reach a critical size. Supposedly, if RNA was contained in one of these droplets, the system could have sparked life.

The article goes on to note:

Evolutionary biologist William Martin of Heinrich Heine University of Düsseldorf, who advocates the idea that life originated in pores in hydrothermal vents, says: ‘It’s not clear to me what real biological system based on observations from nature that this might be emulating.’ However, he adds: ‘If we assume that hydrothermal vents provide a system of organic micro-compartments, and that these have collected hydrophobics, then it’s certainly imaginable that there might have been properties of these droplets in the aqueous phase within a hydrophobic phase that might have been relevant. You never know.’

In origin-of-life theories the term “imagine” appears quite often to cover a giant gulf between what can be demonstrated and what is required to produce the first viable cell.

In this case, the differences between a chemical-rich droplet and a functional cell membrane are numerous. For instance, the latter must distinguish between fuel and waste, allowing only the right molecules to pass into the cell and the right molecules to exit. Even the most generous calculations indicate that the likelihood of droplets coalescing with the needed properties around an extremely rare (nonexistent?) RNA molecule are essentially nil.

In contrast, the appearance of a fantastically improbable set of molecules carefully configured together to achieve a function goal shows the unmistakable signs of intelligent design, a source of causation we know well from daily experience. Design, unlike unguided chemical processes, requires no strenuous exercise in imagination.

Photo: Strawberry Fields, Central Park, NYC, by Damzow (Own work) [GFDL or CC BY-SA 4.0-3.0-2.5-2.0-1.0], via Wikimedia Commons.