A recent study has significantly altered the understanding of early human ancestors, particularly questioning the established view of Homo habilis as the first adept toolmaker. Nearly two million years ago, the remains of a young ancient human were discovered near a spring by a lake in present-day Tanzania. These fossilized bones were unearthed in 1960 and subsequently defined Homo habilis as the earliest known representative of our genus. Researchers have identified the initial examples of the genus Homo primarily by their larger brain sizes and, occasionally, their smaller teeth in comparison to earlier ancestors such as the australopithecines, with the most renowned being Lucy.
According to current knowledge, there were at least three species of early humans: Homo habilis, Homo rudolfensis, and the well-documented Homo erectus. At least one of these species created archaeological sites where they gathered, shared food, and manufactured some of the earliest stone tools, dating from approximately 2.6 to 1.8 million years ago. The artifacts discovered in these locations indicate a greater cognitive complexity in early Homo than what has been observed in any nonhuman primate. For instance, at the Nyayanga site in Kenya, anthropologists have recently found evidence that early humans transported tools over distances of up to 8 miles, suggesting advanced planning and forethought.
Traditionally, paleoanthropologists have regarded Homo habilis as the first large-brained human species responsible for the earliest tool sites. This narrative posits that Homo habilis was the ancestor of the even larger-brained Homo erectus, whose descendants eventually evolved into modern humans. This perspective appeared valid until recent discoveries began to challenge its foundation. In 2015, a hand bone estimated to be 1.85 million years old was discovered at Olduvai Gorge, the same location where the original Homo habilis fossils were found. Unlike the juvenile Homo habilis hand, this bone appeared to belong to a larger, more modern human species: Homo erectus.
Over the past decade, additional findings have pushed back the earliest known dates for Homo erectus to around 2 million years ago in South Africa, Kenya, and Ethiopia. Collectively, these discoveries imply that Homo erectus may be slightly older than known Homo habilis fossils, suggesting that the human lineage is more complex than previously thought. The question arises whether Homo habilis truly gave rise to Homo erectus or if their relationship is more intricate, indicating a “bushy” family tree.
These findings prompt further inquiries into the behavior of early humans at the archaeological sites of Olduvai Gorge. To investigate whether Homo habilis was a predator or prey, researchers examined evidence of animal consumption at the site, where early humans were found to have hunted animals as large as gazelles and zebras. This suggests a form of “central provisioning place,” akin to modern campsites, dating back 1.85 million years. It is the earliest evidence of regular meat consumption and indicates that early humans acted primarily as predators rather than prey.
In the food web, apex predators like lions are rarely preyed upon by other carnivores. If Homo habilis was obtaining large animal carcasses through hunting or by scavenging from lions, it would imply they were capable of managing predation risks, as hunters typically do not become prey. However, if Homo habilis was not yet at the top of the food chain, they might have been vulnerable to attacks from carnivorous species like leopards, which are known to hunt primates.
To determine the nature of the predation on Homo habilis remains, researchers employed artificial intelligence. They trained AI on numerous microscopic images illustrating tooth marks left by contemporary African carnivores, including lions, leopards, hyenas, and crocodiles. The AI successfully identified distinctions between the marks and classified them accurately. The results indicated that the tooth marks on Homo habilis bones correspond with those made by leopards, reinforcing the notion that these early humans may have been prey rather than hunters.
This research fundamentally challenges the long-held belief that Homo habilis was the first skilled toolmaker and hunter. The only complete skeleton of this species found at Olduvai Gorge belonged to a small individual, approximately 3 feet tall, still exhibiting traits suited for climbing trees, which does not align with the image of a proficient hunter. If Homo habilis was not responsible for these complex behaviors, it raises questions about the actual role of Homo erectus in these activities and the evolutionary origins of both species.
Future research at sites like Olduvai Gorge aims to uncover these mysteries and further clarify the evolutionary paths of early humans.
