Late Pliocene environmental change during the transition from Australopithecus to Homo

Area of Science:

• Paleoanthropology
• Paleoclimatology
• Paleoecology

Background:

• The transition from Australopithecus to Homo in East Africa is hypothesized to be linked to arid environmental changes near the Plio-Pleistocene boundary.
• However, data from the latest Pliocene are scarce, limiting our understanding of these environmental shifts and their impact on hominin evolution.

Purpose of the Study:

• To reconstruct late Pliocene environmental conditions in the lower Awash Valley (LAV), Ethiopia, and the Turkana Basin.
• To investigate the environmental context of the emergence of Homo around 2.8 million years ago.
• To assess potential dietary changes associated with the emergence of Homo.

Main Methods:

• Stable carbon isotope analysis of mammalian fauna and pedogenic carbonates from the Ledi-Geraru site in the LAV.
• Mammalian community composition analyses from the LAV and Turkana Basin.
• Comparison of environmental data between the LAV and Turkana Basin during the late Pliocene.

Main Results:

• The LAV experienced increasingly C4-dominated, arid, and seasonal environments from the mid- to late Pliocene.
• Environmental conditions in the LAV contrasted with the more woody and mesic environments of the Turkana Basin during the same period.
• The early Homo mandible (LD 350-1) exhibited a carbon isotope value similar to Australopithecus, suggesting no significant dietary shift during the emergence of Homo.

Conclusions:

• The emergence of Homo around 2.8 million years ago occurred during a period of significant environmental change in the LAV, characterized by increasing aridity.
• Despite regional environmental shifts, the initial emergence of Homo may not have been driven by a dietary adaptation to arid conditions.
• Contrasting environmental conditions between the LAV and Turkana Basin highlight regional heterogeneity during the Plio-Pleistocene, impacting hominin evolutionary pathways.