If you crossed paths with Homo ergaster on an East African plain some 1.5 million to 2 million years ago, its silhouette might look a bit familiar. Long legs, a narrow torso, and a heat-adapted frame that suggests a species built for covering large tracts of open ground.
Many paleoanthropologists view Homo ergaster, meaning “working man,” as a turning point in our evolutionary story. That’s because it shares much of the modern human body plan that we recognize in ourselves today. Still, H. ergaster remains a hotly debated scientific topic. Some researchers argue it was merely the African version of the previously discovered Asian Homo erectus. While others believe H. ergaster deserves recognition as a separate species entirely.
But no matter what it was taxonomically, exploring the story of H. ergaster can teach us about one of the most pivotal chapters in our human evolutionary journey.
Read More: Which Animals Did Early Humans Mainly Hunt?
Homo Ergaster Discovery
First proposed as a unique species in 1975, researchers typically place H. ergaster in Africa during the Early Pleistocene, about 1.9 million to 1.4 million years ago. They estimate that individuals stood somewhere between about 5 and 6 feet tall and weighed between roughly 100 and 150 pounds as adults. That’s a big step up from earlier hominins like Australopithecus, who were shorter, stockier, and better adapted to climbing than walking.
Discovered in East Africa in 1984, one of the clearest windows into ergaster anatomy is the fossil specimen KNM-WT 15000, more commonly known as Turkana Boy. Researchers discovered this 40 percent complete adolescent male skeleton near Lake Turkana in Kenya, and they dated it to about 1.5 to 1.6 million years old. The proportions look surprisingly modern, with long limbs and relatively narrow shoulders.
Some scientists argue that ergaster is simply the African form of early Asian Homo erectus. Others keep ergaster separate based on traits like cranial shape and bone thickness. And as Professor Chris Stringer, a paleoanthropologist at the Natural History Museum in London, says, “I don't think the ergaster/erectus dichotomy really captures the variation in what is normally called Homo erectus, but this needs further research.”
Early Human With Bigger Brains, Smarter Tools
One of the defining features of H. ergaster is the size of its brain, which averaged around 850 cubic centimeters. That is notably larger than those of earlier hominins, but still significantly smaller than those of modern humans, whose brains average about 1,350 cubic centimeters.
The boost in brain power that came with even modestly larger brains likely fueled important behavioral shifts, too. For instance, H. ergaster appeared alongside the earliest Acheulean stone tools in East Africa, which show up around 1.6 million years ago. Unlike the simpler Oldowan stone tools that came before, more advanced Acheulean handaxes and cleavers demanded foresight, symmetry, and refined skills to produce.
Whether you label these advanced tool makers as African H. erectus or H. ergaster, the stone tool industry they created endured for more than a million years.
Where Do These Early Humans Really Belong?
Classifying the earliest members of our genus has never been easy. And as more and more fossils come to light, they answer certain questions while raising others. Some researchers lumped early fossil finds from both Africa and Asia under the umbrella term Homo erectus. But not everyone agrees that’s the best way to organize things.
“I think there is a group of derived fossils from China and Java that can be called Homo erectus. There is a second group of more primitive African fossils that includes the type specimen of ergaster, plus fossils like KNM-ER 3733 and Turkana Boy, that can be called ergaster,” Springer says. “Then there are distinct and even more primitive fossils like those from Dmanisi [Republic of Georgia] that don't belong in either species in my view, and perhaps not even in the genus Homo, but what to call them needs further careful research.”
The Big Picture
Whatever we call it, H. ergaster stands near the root of a pivotal transition in human history. Here is a hominin with a modern-leaning body, a larger brain relative to earlier ancestors, and a more capable toolkit.
“In my view,” Stringer says, “ergaster and erectus as thus narrowly diagnosed represent species that were anatomically fully committed to life on the ground and to a fully human niche in a way that the others were not.”
This commitment to a terrestrial lifestyle, combined with a versatile new toolkit, likely allowed H. ergaster to exploit a broader range of habitats and resources than any of its predecessors.
The names of our ancestral branches may continue to change as new fossils and technology come to light. But the broader story holds true. By roughly 2 million years ago in Africa, a long-legged, heat-tolerant humanoid species was on the scene, and our evolutionary trajectory was already bending toward the modern bodies, brains, and behaviors that we recognize today.
Read More: Early Humans May Have Used Fires to Smoke Meat One Million Years Ago
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- Australian Museum. Homo erectus
- Australian Museum. Homo ergaster
- University of Cambridge. Height and weight evolved at different speeds in the bodies of our ancestors
- Smithsonian National Museum of Natural History. Australopithecus afarensis
- Monash University. Genera Australopithecus and Homo
- Smithsonian National Museum of Natural History. KNM-WT 15000
- Australian Museum. Larger brains
- University of Missouri. Oldowan and Acheulean Stone Tools
- Britannica. Oldowan industry
- Natural History Museum. Homo erectus, our ancient ancestor
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