Changes in hominid facial size and shape over time are not just significant for taxonomic and evolutionary relationships; they also indicate vital functional adaptations. Recently recovered and well-preserved, the Australopithecus skulls, especially the 3.67-million-year-old StW 573, commonly referred to as “Littlefoot,” discovered in Sterkfontein, South Africa, have greatly enriched the fossil record. Although StW 573 is nearly complete, post-depositional damage has resulted in some displacement and fragmentation of the facial skeleton. In a groundbreaking new study, paleoanthropologists set out to digitally reconstruct the surface of StW 573.

The Littlefoot fossil was uncovered in 1994 in a cave in Sterkfontein, South Africa.

This specimen, also known as StW 573, got its name from the four small leg bones discovered amidst a box full of animal fossils that ultimately led to the skeleton’s recovery.

In the 2010s, paleoanthropologist Ronald Clark suggested that Littlefoot might belong to Australopithecus prometheus, while others argued for Australopithecus africanus, a hominid species found at the same site, or even a distinct species within the Australopithecus genus.

Although many aspects of StW 573’s skeleton have been extensively studied, the face has been distorted due to millions of years of geological processes, making physical reconstruction methods ineffective.

In a recent investigation, Dr. Amélie Baudet of the Universities of Poitiers and the University of the Witwatersrand, along with her team, digitally reconstructed the facial bones, producing one of the most complete Australopithecus faces to date.

The researchers evaluated nine facial linear measurements and applied 3D geometric morphometry to compare Littlefoot with various extant great apes and three other Australopithecus fossils.

Findings indicated that Littlefoot’s overall facial size, eye socket shape, and general facial structure bore more resemblance to East African fossils than to younger South African specimens, a counterintuitive result given the lack of complete facial fossils for comparison.

“Given Littlefoot’s geographical origins, this pattern is unexpected and implies a more dynamic evolutionary history than previously believed,” remarked Dr. Baudet.

“For instance, Littlefoot may represent a lineage closely linked to East African populations, whereas later South African hominins developed more distinct facial features through regional evolutionary mechanisms.”

The study also uncovered evidence of selective pressures acting on the orbital region (around the eyes), potentially related to shifts in visual capabilities and ecological behaviors.

“Although our study is limited to a single anatomical region and a small number of comparative fossil specimens, it enriches our understanding of the links between Australopithecus populations across Africa, indicating that the orbital region may have been under evolutionary pressure during that time,” said Dr. Baudet.

“Human facial evolution suggests that our faces have become less prominent and more adaptable over time, but the timeline and inherent evolutionary mechanisms remain elusive.”

Professor Dominic Stratford from the University of the Witwatersrand and Stony Brook University commented, “This study challenges the idea that early human evolution took place in isolated regions. Instead, it supports the concept of Africa as a unified evolutionary landscape, where populations adapted to ecological pressures while remaining interconnected through common ancestry.”

“The face is crucial for primates’ interactions with their environment, serving essential functions in digestion, vision, respiration, smell, and nonverbal communication.”

“In this light, the face is an essential anatomical area for understanding how humans have adjusted and interacted with their surroundings.”

“With only a handful of Australopithecus fossils preserving nearly complete facial structures, Littlefoot offers a rare and invaluable reference point,” asserted Dr. Baudet.

“The anatomical regions of Littlefoot’s face associated with vision, respiration, and feeding will provide further vital insights into our evolutionary history.”

The study results were published in this month’s issue of Comptes rendus palevol.

_____

Baudet, A. & others. 2026. Virtual reconstruction and comparative study of the face of StW 573 (“Little Foot”). Comptes rendus palevol 25(3):43-56; doi: 10.5852/cr-palevol2026v25a3