Study Reveals Early Human Ancestors Were Surprisingly Slow Runners

For years, scientists have debated how exactly Lucy, one of humanity’s most famous ancestors, moved.

Lucy refers to a member of the species Australopithecus afarensis, an early bipedal ancestor of modern humans who lived approximately 3.2 million years ago. Standing at just 1.1 meters (3 feet 7 inches) tall, she was both bipedal and partially arboreal. Discovered in 1974 in Ethiopia’s Afar region by American paleoanthropologist Donald Johanson and his French colleagues, Lucy remains a key piece of the puzzle in understanding human evolution.

New Research Simulates Lucy’s Running Ability

Recent computer simulations have shed light on how fast Australopithecus afarensis could actually run, revealing that these early human ancestors were not particularly speedy. According to an article by biomedical sciences lecturer Tom O’Mahoney, published on terra.com.br, researchers used anatomical modeling to estimate their top running speeds.

A Scene from Three Million Years Ago

O’Mahoney paints a vivid picture of life in prehistoric Africa:

Imagine a scene, about three million years ago, in what is now East Africa. By a river, a wounded antelope collapses, breathing its last. Soon, hyenas descend upon the carcass, fighting with a crocodile that attempts to claim a share. The crocodile retreats, managing only to snatch a leg of the antelope, while the victorious hyenas feast and then wander off.

Then, a group of strange-looking primates approaches, walking upright. They carry objects resembling sharpened stones. They hurriedly cut pieces of meat and begin eating. Before long, they attract the attention of a massive Homotherium—a now-extinct saber-toothed cat—which silently stalks them before launching an ambush. Can these unusual apes escape in time? Can they run fast enough to avoid becoming prey?

How Fast Could Australopithecus afarensis Run?

To answer this question, scientists reconstructed the anatomy of Australopithecus afarensis and simulated its movement. The nearly complete skeleton of Lucy—a global icon of early bipedalism—provided crucial data. Her discovery in Ethiopia in 1974 was groundbreaking, confirming that walking upright preceded brain expansion in human evolution.

Initially, some researchers speculated that Australopithecus afarensis shared a common ancestor with humans, gorillas, and chimpanzees. However, that theory has since been debunked. Scientists now believe that knuckle-walking evolved independently in different ape species, explaining the subtle anatomical differences in their hands and elbows.

More recently, the discussion has shifted to whether Australopithecus actively hunted or primarily scavenged meat left behind by predators. To successfully hunt, early humans needed two key abilities: the speed to chase prey and the endurance to run long distances.

This hypothesis, known as “persistence hunting,” suggests that long-distance running played a crucial role in human evolution. However, scientists believe this behavior only emerged later, coinciding with the more modern anatomy seen in Homo erectus, who lived between 2 million and 1 million years ago.

Lucy Wasn’t Built for Speed

According to the study, the simulated top speed for Australopithecus afarensis was only 11 mph (17.6 km/h), with a minimum running speed of about 3.35 mph (5.36 km/h). In comparison, elite sprinters can exceed 20 mph (32 km/h), while even average runners can reach speeds of around 17.6 mph (28 km/h). This suggests that Lucy and her kind were not well-equipped for high-speed chases or prolonged running.

O’Mahoney concludes that it is unlikely Australopithecus afarensis engaged in persistence hunting, unlike later Homo species. Referring back to his vivid prehistoric scene, he notes:

“Returning to our story, it’s likely that these Australopithecus individuals wouldn’t have escaped the saber-toothed cat. They simply weren’t fast enough or capable of sustained running to evade such a predator.”

The Evolution of Human Running

This study reinforces the idea that endurance running and increased speed only became evolutionary advantages with the emergence of Homo erectus. The ability to run efficiently over long distances may have given early humans a critical edge in both hunting and survival, marking a pivotal step in our evolutionary journey.