Bonobos

Discovery

The earliest description of a wild bonobo is from the 1641 journal of a Dutch anatomist, Nicolas Tulp. His observation of what was thought to be a small chimpanzee includes a description of toes that are webbed between the second and third digits. This trait is common among bonobos, but not chimpanzees.

The first-known captive bonobo lived for only 6 years, from 1911 to1916, and died of pneumonia in the Amsterdam Zoo. Mafuca, as he was named, was being raised with an infant chimpanzee. In 1916, the Dutch naturalist Anton Portielje suspected that Mafuca was not a chimpanzee, but it was not until 1929 in a Belgium museum, that what was thought to be an infant chimpanzee skull was more closely examined. Due to the suture closure, German anatomist Ernest Swarby determined the skull could not possibly belong to an infant chimpanzee. Swarby accurately assigned bonobos to their own species based on these observations.

Robert Yerkes is also credited with early observations of the unchimpanzee-like characteristic differences in the bonobo he worked with, named “Prince Chimpsky.” Yerkes described the bonobo as more gentle, graceful, and intelligent than any chimpanzee he had ever known.

During the 1930s, Eduard Tratz and Heinz Heck at the Hellabrunn Zoo in Munich conducted the first comparative study of chimpanzees and bonobos. Their list of trait comparisons is still relevant. Alison and Noel Badrian began studying wild bonobos in 1974 in the Lomako forest, which is still a study site. In the same year, Takayoshi Kano from Kyoto University began studies in Wamba, the most productive study site also still in use.

Anatomy

Chimpanzees and bonobos are human's closest living relatives, sharing more than 98% of the same DNA. We are not more closely related to one or the other. Our lineages separated about 6million years ago. We are also their closest relatives of all of the living primates. Bonobos and chimpanzees are thought to have shared a common ancestor from whom they split approximately 3 million years ago.

Bonobos are commonly called “pygmy chimpanzees”; however, the overall size difference is negligible. The basic anatomy is the same. The average male bonobo weighs only a few pounds less than the average male chimpanzee. This point is especially true when bonobos are compared with smaller-stature colonies of chimpanzees, like those who live in Gombe, Africa.

There is less sexual dimorphism, size difference between males and females, in bonobos than chimpanzees. A female bonobo's weight is approximately 85% that of her male counterpart, which is the same difference as in humans.

The main anatomical difference between bonobos and chimpanzees is in limb length, head size, hairiness, and upright ability. Bonobos have longer and more slender limbs, a longer torso, and a leaner, more gracile appearance than chimpanzees. The head of a bonobo is smaller than the head of a chimpanzee, and they have a crop of longish black hair with a central part. Bonobo infants are born with dark-skinned faces, compared with the pale appearance of chimpanzee newborns.

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