StW 573 Australopithecus prometheus: Its Significance for an Australopith Bauplan

Area of Science:

• Paleoanthropology
• Primate Paleontology
• Evolutionary Biology

Background:

• The StW 573 skeleton (Australopithecus prometheus) is a remarkably complete early hominin fossil (3.67 Ma).
• Understanding hominin locomotor behavior requires integrating fossil anatomy with paleoenvironmental data (ecomorphology).
• Previous studies have not consistently used ecomorphology to frame evolutionary biomechanical interpretations.

Purpose of the Study:

• To reconstruct the potential niche and locomotor behaviors of the StW 573 individual.
• To explore the concept of a common Australopithecus 'bauplan' by comparing StW 573 with contemporary australopiths.
• To analyze the evolutionary trajectory of hominin bipedalism from early Australopithecus to modern humans.

Main Methods:

• Collation of anatomical evidence from StW 573 and comparative fossil specimens (Australopithecus anamensis, Australopithecus afarensis).
• Virtual experiments on extinct species and biomechanical analyses of extant great apes.
• Analogical experiments using human subjects to study locomotor adaptations.

Main Results:

• Early Australopithecus species, including StW 573, were likely arboreal and woodland-dwelling, relying on tree resources.
• Habitual locomotor mode for all australopiths was upright bipedalism, both terrestrial and arboreal.
• Later australopiths evolved increased terrestrial adaptations, while modern humans further specialized in striding bipedalism.

Conclusions:

• The StW 573 fossil provides crucial insights into early Australopithecus ecology and locomotion.
• Australopithecus locomotion was characterized by versatile upright bipedalism, adapted to both arboreal and terrestrial environments.
• The common panin-hominin ancestor was postcranially more similar to Gorilla than to Pan.