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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They say space is the final frontier, but what if it's just the beginning of our explorations

and experimentation, and what if some experiments require entire galaxies to conduct them?

The galaxies to conduct them.

We often speculated about alien life and alien civilizations on this show, and we take only three things for granted about their behavior.

First, that they evolved someplace where nature was as cutthroat as our own

world, and thus they are not wimps, but are out of the product of eons of survival and adaptation,

that they rose to the top of their world to dominate as we have, and that they made it out in space

they first did so by climbing to the top of a pile of skulls, billions of years deep.

Second, we assume they must have a strong survival urge to have done this and thus care

about their own survival more than that of other civilizations.

This might vary from a deep willingness to sacrifice for their tribe or hive to utter personal

selfishness, no friend or family ties, and it might vary from a species

that would risk its own neck to help other species to one that would go a million light

years out of the way just to incinerate another species' homeworld, but they will care more

about their own survival than ours, for instance.

And third, they will assume anyone in the encounter out in the galaxy will be the same, tough,

and survival-oriented.

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