How does the principle of mediocrity support the search for extraterrestrial intelligence?

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artist's conception of Kepler-186f — extraterrestrial intelligence An artist's conception depicts Kepler-186f, the first Earth-sized extrasolar planet found in its star's habitable zone.

The principle of mediocrity is a foundational concept in the search for extraterrestrial intelligence. Rooted in the work of Nicolaus Copernicus, this principle posits that the Earth and our solar system are not unique or unusual in any significant way.1

By extension, this suggests that the biological and evolutionary processes that resulted in human intelligence on Earth are likely not singular events. The argument relies on three key assumptions:
* Planets capable of supporting life are common throughout the cosmos.1
* Life will naturally emerge on such worlds.1
* Natural selection will, at least occasionally, drive the evolution of intelligent species.1

While astronomers have confirmed that Earth-sized planets within the habitable zone are common—largely thanks to missions like the Kepler satellite—the latter two assumptions remain subjects of ongoing scientific investigation. Researchers continue to seek evidence of biological activity through space telescopes and space probes to validate these claims.1