Ancient Footprint and Tooth Chemistry Reveal Peaceful Coexistence of early Hominids
New research published in Nature sheds light on the surprisingly peaceful coexistence of two early human ancestors in Ethiopia 3.4 million years ago: Australopithecus afarensis – the species famously represented by the “Lucy” fossil – and a more primitive hominid species currently referred to as Australopithecus sp. This discovery challenges the customary linear view of human evolution, suggesting a more complex and diverse prehistoric africa.
The study centers around the Burtele foot fossil (BRT-VP-2/73), discovered in Ethiopia and dating back 3.4 million years. This fossil, comprised of fragments from the first four toes, reveals similarities in big toe structure to that of a gorilla, indicating a greater reliance on arboreal (tree-dwelling) locomotion. Researchers found that Australopithecus afarensis spent less time in the trees, suggesting a developing specialization in terrestrial movement. This difference in locomotion represents the first indication of an ecological partition between the two species.
To further understand how these closely related hominids could coexist without meaningful competition, the research team analyzed carbon isotopes preserved within fossilized teeth. These isotopes serve as a record of ancient diets. The analysis revealed a clear separation in ecological niches. A. afarensis exhibited a flexible diet,consuming both C3 plants (characteristic of cooler,wetter environments) and C4 plants (which flourish in warmer,drier conditions). This dietary adaptability likely aided in navigating the climatic shifts of the Pleistocene epoch.
In contrast, Australopithecus sp. subsisted almost entirely on C3 plants. This dietary profile closely resembles that of earlier Australopithecus species like A. ramidus and A. anamensis, suggesting a more conservative lifestyle focused on forested and humid environments.
This ecological specialization explains the apparent lack of direct competition between the two species. While A. afarensis descendants ventured into open landscapes and broadened their diets, Australopithecus sp.continued to utilize traditional arboreal niches, relying on forest resources that their neighbors were increasingly leaving behind. Researchers describe the situation as analogous to two restaurants side-by-side: one offering diverse cuisine, the other specializing in traditional recipes, each attracting a distinct clientele.
Remarkably, these two hominid groups lived less than 5 kilometers apart. The discovery disrupts the notion of a simple, linear progression in human evolution, where one species consistently replaced another. Rather, it paints a picture of prehistoric Africa as a mosaic of hominids employing varied survival strategies and coexisting peacefully due to their differing adaptations. This diversity, the researchers suggest, may have been the norm throughout much of our evolutionary history.
