How life began on Earth is one of science’s biggest unanswered questions—or at least, that’s how it’s usually framed. In reality, there is an explanation most scientists broadly agree on. But what if that explanation is incomplete? One scientist, using real research and real data, has publicly argued exactly that. And he doesn’t stop there. He’s also put forward another possibility. Yes…aliens. And he isn’t the first scientist to say it either.

The leading explanation for how life began is known as abiogenesis. It proposes that life emerged naturally from non-living chemical processes on early Earth, driven by energy, time, environmental conditions, and increasingly complex molecular interactions that eventually crossed the threshold into biology.

Abiogenesis gained acceptance because scientists have repeatedly demonstrated that many of life’s fundamental building blocks can form without biology. Amino acids, lipids, and nucleotides have all been created in laboratory experiments designed to replicate conditions believed to exist on early Earth.

The theory explains how simple chemical compounds could gradually become more complex over long periods of time. It aligns with what scientists know about early oceans, volcanic activity, atmospheric chemistry, and natural energy sources, as well as fossil evidence showing life emerged billions of years ago.

Despite decades of research, scientists have not recreated the full transition from chemistry to the first self-replicating organism. The precise mechanism that crossed the line from non-living molecules to living systems remains unknown and is still actively debated in origin-of-life research.

Read More: An actual scientist says that aliens may have started life on Earth and he isn’t the only one