4.4-Million-Year-Old Ankle Holds Clues to How Our Ancient Ancestors Walked
New research gives weight to the idea that humans evolved from a species similar to African apes. And it all comes down to the ankles.
Humans stand out – literally – from other primates thanks to our preference for walking on two legs. Although bonobos, chimpanzees, and other species of apes sometimes walk on their hind limbs, this is not their predominant mode of movement. As such, the transition from walking on four limbs (quadrupedalism) to walking on two feet (bipedalism) is considered a crucial moment in our evolutionary journey.
Now, a study published in the journal Communication biology highlights evidence suggesting that an ancient hominid possessed morphological features similar to those seen in gorillas and chimpanzees today, as well as features indicative of an early form of bipedalism. This sheds light on the evolution of bipedalism and “directly narrows the range of explanations for the origin of our lineage,” the researchers write in the study.
Learn more: Were hominids present in Europe 6 million years ago? The imprint finds sparks in the debate
Ardipithecus ramidus: A real kind of transition
Between 1992 and 1994, a team of paleoanthropologists digging in the Afar region of Ethiopia discovered the first remains of an ancient species called Ardipithecus ramidus — an omnivorous creature that climbed through trees and wandered through the forests of Africa 4.4 million years ago, more than a million years before its more famous relative “Lucy” (Australopithecus afarensis).
The discovery of a new species is a great opportunity in itself, but finding ramid was particularly important because of its place in our family tree. ramid is the only hominid (to our current knowledge) to have existed at this time and some researchers believe that it could be an ancestor of Australopithecuswhich is itself considered an ancestor of the genus Homo.
Since 1992, the team has discovered fossils belonging to around 35 individuals. By far the most impressive is a partial skeleton belonging to a female, first described in 2009. The individual (nicknamed “Ardi”) is estimated to weigh about 50 kilograms (about 110 pounds) and measure about 120 centimeters (about 47 inches).
“One of the surprises of this discovery was that Ardi walked upright, while retaining many ape-like features, including a grasping foot,” lead author Thomas Prang, assistant professor of biological anthropology in Arts and Sciences at Washington University in St. Louis, said in a statement.
The fact that it combines characteristics common to apes such as chimpanzees and gorillas as well as those observed in human ancestors makes ramid “a real kind of transition,” Prang said.
Three decades after the initial discovery, Ardi continues to be one of the oldest and most complete hominid skeletons discovered to date.
Comparison of primate foot bones
In this new paper, Prang and his team compared Ardi’s ankle bones to those of apes and early humans, specifically the talus (an ankle bone that meets the tibia (tibia) and fibula (calf bone)) and the calcaneus (the heel).
Interestingly, Ardi’s ankle had a unique blend of features incorporating features seen in African apes and those suggesting bipedal movement. The positioning of the talus, for example, shows “a more African ape-like ankle posture” that could have favored movements such as vertical climbing.
“Collectively, these results are inconsistent with the evolution of humans and chimpanzees from a generalized arboreal ancestor that lacked adaptations for terrestrial quadrupedalism, vertical climbing, and suspension,” the study authors wrote.
Prang describes these findings as a “correction”, correcting previous interpretations that did not recognize Ardi’s connection to apes like chimpanzees and gorillas, and instead thought the skeleton provided evidence of a more generalized ancestor.
“Based on their analysis, they concluded that living African apes – like chimpanzees and gorillas – are like dead ends or dead ends of evolution, rather than stages of human emergence,” Prang said. Instead, he says, it suggests that the last common ancestor we shared with chimpanzees shared some similarities with chimpanzees living today.
Learn more: Humans evolved from a common ancestor that appeared 6 million years ago
Article Sources
Our Discovermagazine.com editors use peer-reviewed research and high-quality sources for our articles, and our editors review the articles for scientific accuracy and editorial standards. See the sources used below for this article:
