I'm sure he's human, but all the main characters in IX are even not human or don't look it.

Zidane = Alien
Garnet = Horned summoner
Vivi = Puppet
Steiner = Uhh, well I guess he looks human, probably just wears alot of make up
Freya = Rat beast
Quina = Qu
Eiko = horned summoner
Amarant = Blue chicken man