“This is one of the big questions that we really don’t know at this point,” says Lena Vincent of NASA’s Jet Propulsion Laboratory in Pasadena, California. “Anyone who says otherwise, I am skeptical.”
That’s not to say there isn’t a shortage of ideas about how life on Earth began. On the contrary, all sorts of hypotheses have been put forward to explain how non-biological chemicals self-assemble into living organisms. Some rely on hypothetical self-replicating molecules, others on clump-like structures that may have been cell precursors, and others focus on complex cycles of chemical reactions.
However, none of these ideas were widely accepted, much less led to definitive experiments. As a result, thinking about the origin of life becomes an exercise in reasoning in uncertainty. It’s about how to distinguish between ideas that are truly promising and those that merely pretend to be plausible.
The truth is, we can never know exactly how life began on Earth, says Vincent. “We don’t have access to any part of this Earth’s history that we can examine.” It’s about showing what we know and what we’re compatible with.
That is why Vincent prefers to talk about “the origin of life” to avoid the implication that we are studying a single, specific event. It “could have happened many times,” she says, and “could continue to happen” somewhere in the universe.
What matters is whether it’s an experiment trying to demonstrate how life works.
