Pentaths are the dominant species of planet Pentathlon. In the distant past they were merely an average race of Humans; however the lack of interesting smells on Pentathlon led them to dispense with noses and evolve third eyes in their place. Because of this some anthropologists debate whether or not they can still be considered true Humans, although most say yes and most non-anthropologists say there are really more important things to worry about.
The number of Pentaths roaming outside their home planet is impossible to determine, as one may easily cover the "extra" eye with a prosthetic nose, either because they feel more acceptable that way or because they are on some sort of undercover mission.