Bonobo (Pan paniscus) Fact Sheet: Physical Characteristics

Body measurements

• Black face, ears, palms and soles of feet; individuals in managed care may have lighter pigmentation.
• Black body hair is long and fine.
  • Many adults retain the white rump tuft common to infants.
  • Hair on top of head appears to be parted down the middle.
  • Side-whiskers are long and thick.
  • Baldness does occur, although "perhaps later in life" than in other chimpanzees. (Groves 1989)
• Compared to chimpanzee:
  • Brow ridges and facial bone structure are less pronounced.
  • Head is more rounded, with smaller ridges above eyes, less developed muzzle, less jaw protrusion..
  • More slender build, narrower chest, bone and muscle of lower limbs is heavier.
  • Ears smaller and almost completely covered by cheek whiskers.
    • Chimps' ears stand out more from the head
  • Molars smaller.
  • Less sexual dimorphism. (Cramer and Zihlmann 1978).
  • Lips are lighter, often reddish colored. (de Waal 2001)
  • Nostrils are "thick-walled" and more gorilla-like. (de Waal 2001).
• In overall size, bonobos are not smaller than chimpanzees (most anatomical measurements overlap) but there are differences in proportion:
  • Bonobos have shorter upper limbs and longer lower limbs (Zihlmann 1996).
  • Compared to chimpanzees, bonobos have body characteristics that are better for bipedal or upright posture: (Myers Thompson 2002)
    • More centrally positioned opening in skull for spinal cord (foramen magnum)
    • Longer feet
    • Longer thigh bones
    • More body weight (heavier muscles) in lower legs of bonobos. (Zihlmann 1984)
  • Bonobos are quite similar in overall body size, cranial capacity, and lower limb length to an ancestral hominid, nicknamed Lucy, who lived some 3 million years ago in Africa. (Zihlmann 1984)

• Of all the great apes, bonobos are the most human-like in their leg length. (de Waal 2001)
• Bonobos share with humans a similar pattern of distribution of brain neuron cells called VENS (also called spindle cells or Von Economo Neurons). (Hakeem et al 2009)
  • VENs help regulate complex social interactions requiring knowledge of other individuals' mental state.
  • Neither gorillas nor chimpanzees have a VEN brain cell organized in clusters like those of humans and bonobos.
  • The only other animals with some form of VEN cells are whales, dolphins, and elephants, all animals with large brains and highly evolved social awareness, including empathy.
• Pygmy chimpanzees show few individual differences in their blood groups (unlike P. troglodytesand humans).
  • Common chimps are either group A or O, and the A antigen of their red cells differs from those in human red cells.
  • Blood group studies show many differences between bonobos and common chimpanzees, enough that some researchers have suggested they should be in a separate genus. (Socha 1984)
• Humans and chimpanzees share at least 98.5% of their DNA.
  • Great apes have 24 pairs of chromosomes
  • Humans have 23 pairs (18 of the 23 pairs are virtually identical)

Bonobos are sometimes confused for chimpanzees, though their facial features, head shape, and long legs for a more upright posture make them quite different.

In terms of the "social parts of their brain," bonobos and humans are most similar among the great apes.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Boesch (2002)
Cramer & Zihlman (1978)
Groves (1989)
Hakeem et al. (2009)
Myers & Thompson (2002)
Socha (1984)
de Waal (2001)
Zihlmann (1984, 1996)