A recent study on the 4.4-million-year-old fossil Ardipithecus ramidus, affectionately called “Ardi,” has given us wonderful, tantalizing new insights. These discoveries tell an extraordinary story of the locomotion, anatomical evolution and subsequent adaptations of our earliest human ancestors. Unearthed in 1994, Ardipithecus ramidus was widely considered one of the oldest and most complete skeletons known to exist. It represents an important period in the development of hominins.
Thomas (Cody) Prang, assistant professor of biological anthropology at Washington University in St. Louis, directed this pioneering study. Read our whole study published in Communications Biology. The research focuses on Ardi’s ankle anatomy. This groundbreaking discovery helps us further understand the movement patterns and behaviors of some of the earliest hominins.
Insights from the Ankle Structure
The ankle of Ardipithecus ramidus indicates adaptations to both vertical climbing and a terrestrial quadrapedalism-the use of all four limbs. These findings mean that Ardi probably climbed more like modern African apes did. Its feet can be inferred to have looked quite similar to those of modern apes. In particular, the bottoms of Ardi’s feet, which included a flexible heel, had to be in contact with the ground as she walked or climbed.
The research team compared Ardi’s ankle to other species including living apes, monkeys, and even early humans. We found amazing things through this comparison. It hinted that the last common ancestor of us and chimps probably looked more like today’s chimp and behaved more like today’s chimp, too.
“It’s important to note that this paper does not imply that humans evolved from chimpanzees,” – Thomas (Cody) Prang
Ardipithecus ramidus is about a million years older than the most famous of all early human ancestor fossils, “Lucy,” another important early human ancestor. The research presented here tells a different story that debunks some commonly held assumptions. It proposes that previous interpretations overstated Ardi’s likeness to modern apes, thereby separating it from its primate kin.
Evolutionary Implications
Cohort to a burgeoning body of research, the study helps bring into focus the way early hominins first adapted to a bipedal form of locomotion. Despite having some features suggesting it was walking upright, Ardipithecus ramidus was still very much an ape. That grasping foot also demonstrates that Ardi was an excellent climber. Yet at the same time, he made the switch to culture shock brought on by life on the ground.
Prang’s analysis shows that, in evolutionary terms, living African apes, such as chimpanzees and gorillas, are best considered evolutionary dead ends. These species are not direct ancestors of modern humans. This worldview fits the mold of previous ideas about the evolution of humanity but further complicates an already rich conversation.
“The finding is both controversial and also aligned with what people thought originally,” – Thomas (Cody) Prang
The study’s findings highlight the need for continued research to bring into focus our evolutionary legacy. By detailing Ardipithecus ramidus’ anatomical peculiarities, paleoanthropologists could piece together the traits that made up our common ancestral legacy.
Ongoing Research and Future Directions
As new research rolls in, concerns linger regarding some anatomical aspects of Ardipithecus ramidus, especially the opposing big toe. Ardi’s toe structure suggests a new type of adaptation. This same design would have facilitated her ability to climb trees and move about on land.
Future studies will hopefully zoom in on this point. They will investigate how these adaptations affected the evolutionary trajectories that produced modern humans. This new study deepens our knowledge of Ardipithecus ramidus. It enhances the broader narrative of human evolution.