By his own account, Bacon completed his first mature painting in 1944, during World War II. Appropriately to the time, he addressed themes not just of suffering but of torment, and drew from a combination of mythological and Christian sources to articulate themes of violent revenge. The mood endured throughout his work, and certainly informed the somber Study of a Baboon.
Bacon often derived his images from photographs—from newsprint and film stills and, notably, a reproduction of a Diego Velázquez painting—and he copied this baboon from one of his favorite books, Marius Maxwell's Stalking Big Game with a Camera in Equatorial Africa, published in 1925. The photographs are chiefly of large wild animals such as the elephant and the rhinoceros, but among the plates is a startling reproduction of baboons in acacia trees. The baboon at the right is perched on a forked tree trunk much like that in Bacon's work. Bacon had traveled often in Africa and was reportedly fascinated to see monkeys and apes of various kinds caged in the parks, while outside others roamed in freedom. Study of a Baboon pointedly incarnates this ambivalence. The baboon is half imprisoned, half free. The vigorously painted bars of the cage force the baboon uncomfortably close to the viewer. Its body is partly transparent and ghostly, but its sinister open maw and glinting white fangs mark a very real presence. Bacon pens the viewer into the enclosure with the ferocious creature, suggesting a close correlation between the two beings.
from The Museum of Modern Art, MoMA Highlights, New York: The Museum of Modern Art, revised 2004, originally published 1999, p. 213