The Koolakamba is believed to be larger, flatter-faced, larger-skulled and more bipedal than a chimp. It may also be a mutation, in which case we are witnessing evolution in action. According to DuChaillu (DuChaillu 1861 and 1969), the physical characteristics described for Koolakamba include a short and broad pelvic structure, large supraorbital ridge, high zygomatic ridges, less prominent "muzzle", dentition in which the upper and lower incisors meet squarely forming a grinding surface, and a larger cranial capacity than that of the common chimpanzee. Much of what DuChaillu records is essentially ethnographic. He includes the indigenous names and lore relevant to the ape, and reveals his own cultural foibles in the writing. His works are classic period pieces with wonderfully descriptive text and presumably accurate illustrations, but limited quantitative (mostly anthropometric) data.
Although there has not been a documented sighting of the Koolakamba or a proof of its existence in modern days, in 1881 Koppenfelds indicated that it does indeed exist: “I believe it is proved that there are crosses between the male Troglodytes gorilla and the female Troglodytes niger, but for reasons easily understood, there are none in the opposite direction. I have in my possession positive proof of this. This settles all the questions about the gorilla, chimpanzee, Kooloo Kamba,....etc.”
In November 1996, a picture of an unusual ape (taken by Peter Jenkins and Liza Gadsby at the Yaounde Zoo, Cameroon) was featured in the Newsletter of the Internal Primate Protection League (IPPL). This picture showed a seemingly hybrid ape with wider face and a larger skull than that of a chimpanzee and smaller than that of a gorilla. The ape in the picture had features that seemed to belong to both the gorilla and the chimpanzee.
Scientifically, the Koolakamba has not been determined to be a subspecies of the chimpanzee, a gorilla-chimpanzee hybrid, or perhaps even a representative of an individual variation. Yerkes reported several "unclassifiable apes" with features intermediate between chimpanzee and gorilla in his 1929 book "A Study of Anthropoid Life". In fact most of these are regional races of chimpanzee classified as separate species by over-enthusiastic naturalists.