Theory: Humans are the origin species.

In DNA Mad Scientist the scientist can find to origin for all of the crew on a big spiral galaxy map except for John. It's possible that the wormhole shot John into the future, in the same galaxy, but long after man had spread out and adapted into all of the other species. That's why they all look human, why the dominant force are the most human, and why they're all upgraded when it comes to things like sight and memory.

It might not hold true but it's a fun idea.