Human bipedalism: A look at its ancient origins

Bipedalism, or the ability to walk upright on two legs, is one of the defining characteristics of modern humans and their ancestors. But how old is this trait that distinguishes us really? Over the past few decades, scientific discoveries have shed light on the long and complex history of human bipedalism, revealing that its origins could date back millions of years.

Fossil Evidence: A Window to the Past

Fossils are the key to understanding how and when human ancestors began walking on two legs. One of the most iconic finds is that of Australopithecus afarensisa species that lived approximately 3.9 to 2.9 million years ago. “Lucy”, the famous partial skeleton discovered in Ethiopia in 1974, is one of the most complete examples of this species. Her bone structure, particularly the pelvis and femur, clearly indicates that she was capable of walking upright.

More recently, the discovery of Sahelanthropus tchadensisa hominid that lived between 6 and 7 million years ago, has pushed the limits of human bipedalism even further back in time. Although only fragments of its skull have been found, the position of the foramen magnum (the hole where the spinal column connects to the skull) suggests that this species could also have walked upright.

Footprints of Laetoli: The Record of a Millennial Walk

One of the most fascinating evidence of early bipedalism comes from the Laetoli footprints, discovered in Tanzania in 1978. These footprints, preserved in solidified volcanic ash, are about 3.6 million years old and were attributed to Australopithecus afarensis. Analysis of the footprints shows bipedal locomotion strikingly similar to that of modern humans, with a clear heel-to-toe pattern and a developed plantar arch.

(Photo: Wikimedia Commons)

Evolutionary Factors: Why Do We Walk on Two Legs?

Bipedalism is not only an anatomical curiosity, but also a key evolutionary milestone. Theories vary as to why our ancestors adopted this form of locomotion. One of the most accepted is that walking on two legs freed the hands to carry food, make tools, and protect themselves. Additionally, standing on two legs allowed early hominids to see further into open savannahs, helping them detect predators or resources.

Another factor could have been energy efficiency. Biomechanical studies have shown that walking on two legs consumes less energy than moving on four limbs, especially over long distances. This would have been advantageous to human ancestors who needed to roam large areas in search of food.

The Future of the Study of Bipedalism

Research on bipedalism is far from over. With the advancement of technologies such as 3D analysis and isotope dating, scientists continue to refine our understanding of this fundamental trait. Each new fossil discovery has the potential to change our perception of how and when bipedalism evolved.

Ultimately, human bipedalism is an evolutionary adaptation that dates back millions of years and has been crucial to our history as a species. By understanding our origins, we not only learn about our past, but we also come closer to unraveling the mysteries of what makes us human.