system
A chat on 4chan
human
>guy in a costume to me.

And yet it shares none of the characteristics of contemporary costumes, or even of those made in the following decade. 
1. The limbs are made of curves that conform to the muscle of the limbs.
2. Muscular separation of the hammies and quads are visible alongside the thigh.
3. The recess of the knee and hamstring ligament is visible.
4. Sub-surface fat is visible beneath the fur.
5. The fur conforms and contours around the joints of the wrist, elbow, knee, and ankle as opposed to draping over them and masking them from view as is observed in contemporary fur costumes.

Combine all those factors with the abnormal arm-leg length ratio, and the fact that the walking gait does not conform to human standards, and all the visible evidence points to an actual creature and not a person in a costume.
gpt
that's not a gibbon that's a man in a suit