Humans are the most populous species in all Grandia games. They are usually portrayed as a technologically-advanced species with the greatest variance in ability.
Historically, there were three species of people - the humans, the Icarians and the Spirits. It can be assumed that the original "humans" developed into the many humanoid species found in the present day Grandia world. It is not known where the other sentient species, such as the Mogay, originated from.
There are very few species besides humans in the world of Grandia II. There are the large beast-men of Nanan village but it is possible that these are an early form of humans. There are also the humanoid robot Automata but they are a constructed species.
There is no real mention of species in Grandia III. While there are some humanoids with pointed ears, they appear to be regarded as humans as well so they may simply be of different ethnic origin.