well several:, pointy ears, uncommon colored eyes for a human, silver hair but still looks young (something possible but also not very common), articles of clothing wouldn't be seen in any period of time known to be occupied by humans, tribal markings on clothing that aren't of any human language, you know stuff like that

the only thing that really would point him out as human would be the shape of his body and that he has hair mainly on his head (the way the hair looks is suppose to seem different too but it's not really a detail you could tell by looking)