Pliocene climatic change and the origins of Homo at Ledi-Geraru, Ethiopia.

Background: Long-term cooling and aridification are associated with the spread of grassland habitats and the appearance of new hominin adaptations starting in the late Miocene. However, limited fossil data during critical periods limits our ability to examine these climatic correlations further.

Aim: We set out to reconstruct potential habitat and climate conditions at the origin of our genus Homo.

Subjects and methods: Mammalian faunal lists and species trait data were collected for Ledi-Geraru localities dated from ∼2.78 to <2.59 million years ago (Ma). These were compared to a modern comparative dataset of mammal communities across Africa with known habitat and climate conditions, as well as to other fossil mammal data from eastern Africa in the time period leading up to and following shortly after the earliest known appearance of Homo at ∼2.78 Ma.

Results: Early Homo is associated with ongoing aridification and increasing seasonality in the Afar Depression. While climate trends in eastern Africa parallel global models, local environmental variation persisted across fossil-bearing regions.

Conclusion: Climatic change (aridification and increasing seasonality) continues to be supported as a possible factor in the origins of our genus, although other fossil hominins continued to persist in these conditions.