Scientists have linked a 3.4-million-year-old foot fossil to the species Australopithecus deyiremeda, confirming it coexisted with Lucy's species in ancient Ethiopia. The discovery reveals differences in locomotion and diet between the two hominins. This association highlights how early human ancestors shared landscapes without direct competition.
In 2009, a team led by paleoanthropologist Yohannes Haile-Selassie from Arizona State University discovered eight foot bones in 3.4-million-year-old sediments at the Woranso-Mille site in Ethiopia's Afar Rift. Dubbed the Burtele Foot, these fossils were described in 2012 and noted for differing from Australopithecus afarensis, the species of the famous Lucy skeleton. At the time, naming a species based solely on postcranial elements was uncommon, so researchers sought cranial remains for confirmation.
By 2015, teeth from the area led to the announcement of Australopithecus deyiremeda, though the foot's direct link remained uncertain due to stratigraphic questions. Over the following decade, additional fieldwork strengthened the connection. 'We now have enough material to confidently link the Burtele foot with the species A. deyiremeda,' Haile-Selassie stated.
The Burtele Foot features an opposable big toe suited for climbing, more primitive than A. afarensis feet, yet it supported bipedal walking, propelling from the second toe rather than the big one. This suggests varied forms of bipedality among early hominins around 3.4 million years ago.
Isotope analysis of 25 teeth by Naomi Levin of the University of Michigan revealed A. deyiremeda's diet leaned heavily on C3 resources like trees and shrubs, contrasting with A. afarensis's mixed C3 and C4 (grasses) intake. 'The isotope data show clearly that A. deyiremeda wasn't accessing the same range of resources,' Levin noted.
A juvenile jaw, estimated at 4.5 years old via CT scans, showed growth patterns akin to other early australopiths, with a disconnect between incisor and molar development. Geological work by Beverly Saylor confirmed the fossils' associations.
These findings, detailed in a 2025 Nature paper, illustrate ecological separation that allowed coexistence. The research, funded by the National Science Foundation and W.M. Keck Foundation, underscores lessons for understanding past and present environmental changes, as Haile-Selassie emphasized: 'If we don't understand our past, we can't fully understand the present or our future.'