WMG / After Man: A Zoology of the Future

Strigers are the ancestors of Tamaranians

They're described in the comics as being descended from a feline race, and the Striger does resemble a primate in proportions, so they could translate well to Human Aliens. Maybe some for whatever reason were taken from earth by aliens for whatever reasons, but due to a Negative Space Wedgie the ship carrying it got thrown back millions of years, and when it got to ancient Okaara (where they were from before migrating to Tamaran), the Strigers formed a breeding population and evolved into several species over time, including a highly intelligent one, and the rest is history.

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