I always personally thought descriptions of Grendel were very much that of a silverback gorilla. Fangs, Fur, Loping gait, strength. Its a pretty good image.
There is a similar idea about Conan and there is a bit of ambiguity in the collected stories of the oc. There are ancient kingdoms and fallen empires of creatures that are described like apes or furless apes, notably gorillas and similar creatures here and there. The inhabitants of these, if they are sane, sometimes call themselves, and are sometimes called either man, or superior to man or degenerate from man. Basically everything from lovecraftian space elves to goblins. Conan himself is quite often described in way that is ambiguous, but certainly includes both things like thick maned, long armed, barrel-chested, and even gorilla like. In particular by some of the people of the kingdoms he visits. Described as black maned, hairy, sometimes to the point of fur, and in his latter years, as with it falling like a coat of silver over his back. Overall its a silly idea. Leaving the racism aside, I think the author intended Armenian or persian. Black haired, golden tanned skin, sometimes with pale golden irises, certainly not white or nordic as often depicted much like some other middle eastern mythical characters of note. A simpler explanation is bad writing and gorillas commonly thought of as the epitome of strong men at the time of the early novels. The stories are mostly set in southern hyperborea i.e. middle africa also lends itself to this. I wonder if this may be why Grendel is like that as well. A popular english translation of Beowulf was made by Tolkien (who grew up in africa) written in the same era as the early Conan? A popular translation makes Grendel more akin to a nordic troll, which is more similar to a bear, weakly supported by aglæca ambiguity which sometimes seems to confuse grendel and beowulf which would make more if the name beowulf even if literally translated to bear, still meant bear hunter/killer or strong as a bear. I'd lean towards tolkien, but it shows how cultural context flavors translation. There is just not much description either, and even without the inevitable translation errors in visual descriptions of things that dont exist, ambiguity caused by bad writing is nothing new.
