Hello, SFIA audio listeners. In this month's Nebula exclusive, big alien theory,

we're asking the reason alien civilizations might be rare is because most aliens are huge.

To hear it and every episode early and ad-free, plus hours of bonus content,

check out go.nebula.tv slash Isaac Arthur and use my code, Isaac Arthur.

What happens when intelligence no longer requires biology, when flesh and bone are left behind,

and civilizations transcend into something new?

For most of history, intelligence has been tied to biology, depend on fragile flesh, finite lifespans, and environmental constraints. Our civilizations have relied on that precarious

intelligence to survive and thrive, but what if a civilization transcends these limitations,

shedding organic forms in favor of something entirely new.

In this episode, we will explore the concept of post-biological civilizations,

societies that have abandoned biological evolution in favor of technological ascension.

And we must ask ourselves if this is a fate humanity may one day embrace.

Would this be a dream come true, or a nightmare yet

to come? Whether through mind uploading into vast digital networks, the creation of fully

autonomous machine intelligences, or the emergence of exotic life forms beyond our current

comprehension, these civilizations may represent the next great leap for intelligent

beings, freed from the constraints of aging, disease, and even the needs for planets or

atmospheres, such entities could spread across the cosmos, evolving in ways unimaginable to biological

minds. The physical presence of post-biological civilizations.

Despite their digital nature, or whatever substrate encoding they use, post-biological

civilizations might still have a significant physical footprint.

Some could inhabit vast megastructures, such as Dyson's swarms or Matriostra brains,

...