The extant Mali cliff range chimpanzees versus Rift Valley early Homo: a parallel evolution hypothesis

Abstract

In this manuscript we hypothesize the existence of parallelism between the evolution of early Homo along the Great African Rift Valley and the evolution of extant Mali chimpanzees. A 2005 discovery found that Pan and Homo lived sympatric to each other ~550 kya, on the savannah eastside of the Great African Rift Valley, where early Homo evolution occurred. Therefore, chimpanzees, not previously known to range along the rift valley, were subjected to the same ecological pressures as early Homo. Our current data on West African Mali cliff-range chimpanzees suggests that their endemism, isolation, eurytopism and cultural diversity result from long-term stressful selective pressures, as described for the East African savannah hominins. We thus hypothesize that Pan, living in marginal habitats of low-resource environments, exhibit shared suite of traits thought unique to early Homo. These pressures culminated in parallel adaptations and survival strategies to cope with limited resources in terms of land use patterns and demographic populational mobility. Furthermore, the cliff-ranges inhabited by present day West African chimpanzees (Pan troglodytes verus) and by the Fulani, Maninka and Dogon tribes, can serve as a model for sympatric Pan-Homo and other contemporaneous hominin taxa. The fossil record indicates that early Homo adaptations were manifested in species radiation and expansion along the rift valley north-to-south. Likewise, we suggest that the ecological stresses along the cliff-ranges induced phenotypic adaptational plasticity and migration also in Mali chimpanzees, resulting in their accelerated hominin evolution. In this manuscript we present comprehensive evidence in support of this hypothesis. 

In memory of conservationist/anthropologist Dr. Jane Goodall, DBE, UN Messenger of Peace; paleo-archeologist Prof. Avraham Ronen; and molecular-geneticist Prof. Morris Goodman, member of the US National Academy of Sciences.
In memory of Thomas Kamissoko, our tribal liaison, local physician, Sagabari, Mali, who made our research possible.