Of the few races that can interbreed, humans have the most success. Unfortunately, this is most often with the Orcs. Orcs, while not evil per se are definitely barbaric and violent, and aren't adverse to 'collecting' mates of other species. Thus, Half-Orcs. As fecund as the Orcs are, its surprising that there aren't more of them. As is, they're numerous enough to almost be considered a race unto themselves; unlike the half-elves, whose numbers have only recently risen.

Note- the colors aren't quite right here- I'm pretty certain there's an issue with the colors as they're seen on my screen as opposed to the artist's screen.

The art is by and the race... Not mine originally, but this variant is!