According to an alternative model of how intelligent life emerges on planets like Earth, the existence of aliens—and human beings–could be the result of natural planetary processes.

A new study rewrites the story of human evolution, suggesting that intelligent life is not rare but a natural planetary process rather than an improbable event.

“Our existence is probably not an evolutionary fluke,” says Jennifer Macalady, a study co-author and microbiology professor at Pennsylvania State University. “We’re an expected or predictable outcome of our planet’s evolution, just as any other intelligent life out there will be.”

Researchers present an alternative to the long-held “hard steps” theory to explain the evolution of complex life, suggesting it’s the natural outcome of a habitable environment rather than a lucky bre