From "Star Trek: The Next Generation: Unnatural Selection (#2.7)"
Chief Medical Officer's log - this will be my final report to the Enterprise: Just as changes in evolution are known to be caused by changes in the environment, we now know the process also works in reverse. An attempt to control human evolution has resulted in a new species. It's lethal to its predecessors. The children will be condemned to live out their lives in isolation. The quarantine of the Darwin Station must be maintained forever!