First fossil chimpanzee

Area of Science:

• Paleoanthropology
• Primate Evolution

Background:

• The fossil record for chimpanzees (Pan) is notably absent, contrasting with abundant hominin fossils.
• Chimpanzee populations are currently restricted to West and Central African forests, while most hominin fossils are found in the East African Rift Valley.

Observation:

• Previous hypotheses suggested climate-driven vegetation shifts and the Rift Valley's geography separated human and chimpanzee ancestral populations.
• These theories aimed to explain human-chimpanzee lineage divergence and the evolution of bipedalism.

Findings:

• The discovery of the first fossil chimpanzee in Kenya's Kapthurin Formation.
• These Middle Pleistocene fossils indicate the presence of *Pan* in the East African Rift Valley alongside extinct *Homo* species.

Implications:

• Challenges the notion that the East African Rift Valley was an insurmountable barrier to chimpanzee occupation.
• Suggests that suitable habitats for both hominins and chimpanzees co-existed in the Rift Valley during the Middle Pleistocene.
• Provides crucial fossil evidence for understanding early hominin and chimpanzee co-existence and evolutionary divergence.