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.

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

This episode is sponsored by Skillshare.

What is a human being?

Every generation our scattered tribes changed, and how much more so when we are scattered

to a million worlds?

Is humanity an identity or a fundamental set of DNA?

So today we'll be looking at the future of humanity in a more literal sense, asking what

might change about us in the generations to come.

This is obviously a bit tricky since we have to consider things like genetic engineering

and cybernetics, or even folks entirely leaving genetics behind

in favor of an uploaded digital life, though we'll save that topic for next week.

It's also worth considering more natural paths, how we tend to evolve if things just stay the

same here on Earth, or how we'd evolve or adapt to different individual worlds we might settle

in the space age.

Critical to the whole notion though is that successful species not only don't stay the same

over generations, but typically diverge into many different species with time.

One could argue there were all the same species as the original animal that presumably

evolved into us and cats and dogs and

insects. This approach to species classification is called clades, tracking the descendants

...