“IT IS one of these big questions that we truly are clueless about at this point,” says Lena Vincent at the NASA Jet Propulsion Laboratory in Pasadena, California. “Anyone who says otherwise, I would be sceptical of.”
Which isn’t to say we are short of ideas for how life on Earth began. On the contrary, all manner of hypotheses have been put forward to explain how non-living chemicals might self-assemble into a living organism. Some rely on hypothetical self-replicating molecules, some on blob-like structures that could have been the predecessors of cells, while others focus on complex cycles of chemical reactions.
Yet none of these ideas has gained widespread acceptance, never mind led to a definitive experiment. As a result, thinking about life’s origins is an exercise in reasoning under uncertainty. It is about how to tell the difference between a truly promising idea and one that merely has a veneer of plausibility.
The truth is that we can’t know for sure exactly how life began on Earth, says Vincent. “We just don’t have access to the part of history on this planet that would allow us to verify that.” The best we can do is to demonstrate processes that produce life and show that they are compatible with what we know about the early Earth.
For that reason, Vincent prefers to talk about “origins of life”, to avoid implying that we are studying a single, specified event. It “may have happened many times”, she says, and “may be continuing to happen” somewhere in the universe.
What is important is whether an experiment seeking to demonstrate how life …