The air with its 30 percent oxygen content was poisonous to unmodified humans.

Nor indeed were many unmodified humans nearly as robust as the cadets had long since become.

"I'm setting up the model to treat Commensals and unmodified humans as separate but interacting populations."

I have no information on troll physiology, but I suspect that their reaction times are slightly faster than unmodified humans.

It deals with the creation of the "Quaddies", genetically modified people who have four arms, the second pair appearing where unmodified humans would have legs.

For instance, their bones were stronger than unmodified humans.

Their lungs extract oxygen more efficiently than normal unmodified humans, allowing them to exert themselves without getting short of breath, or function at high altitudes.

There are the unmodified humans, who are the ones who colonize planets.

These bodies are extensively genetically altered, so much that they can't breed, either between themselves or with unmodified humans.

The first colonists landed in 2073, and they were unmodified humans.