A team of paleoanthropologists has made a groundbreaking discovery about the body shape of Homo erectus, one of humanity’s most significant ancestors. Contrary to the long-held belief that this species was lean and athletic, designed for long-distance running and endurance activities, new findings suggest that Homo erectus actually had a stockier build. This shift in understanding significantly alters how we view the evolution of the human body, suggesting that the shape of modern humans emerged much later in our evolutionary history than previously believed. The study, which centers around the fossilized remains of Homo erectus known as the Turkana Boy, has been published in the latest issue of Nature Ecology and Evolution.
The fossil of the Turkana Boy, discovered in 1984 near Lake Turkana in Kenya, is one of the most complete and important early human skeletons ever found. This 1.5-million-year-old specimen has provided scientists with valuable insight into the physical characteristics and possible lifestyle of Homo erectus, one of our most direct ancestors. However, the new study challenges long-standing assumptions about its body structure. The findings, led by Markus Bastir from Madrid’s Museo Nacional de Ciencias Naturales and Daniel García-Martínez of the Centro Nacional de Investigación sobre la Evolución Humana in Spain, reveal that Homo erectus had a ribcage that was significantly deeper, wider, and shorter compared to that of modern humans.
This shape of the ribcage suggests that Homo erectus had a much stockier and more robust physique than researchers had previously envisioned. The modern human body, with its relatively narrow pelvis and ribcage, may not have evolved until much later, likely with the emergence of Homo sapiens. According to Scott Williams, associate professor at New York University’s Department of Anthropology and co-author of the study, the modern human body shape—characterized by a flat, tall chest, narrow pelvis, and rib cage—likely did not develop until the appearance of Homo sapiens. The findings suggest that the fully modern body type was a much more recent evolutionary development than once thought.
The new research indicates that Homo erectus was probably not the long-distance runner we often imagine it to be. Fred Spoor, the study’s senior author from London’s Natural History Museum, argues that the iconic Homo erectus was likely less athletic and lean than previously portrayed, as the evidence suggests that its build was more robust, with a more voluminous thorax. These conclusions are consistent with recent fossil discoveries, which show that the species may have had a larger body mass than once estimated. This revision of Homo erectus‘s physical capabilities may also suggest that the adaptations we associate with endurance running in modern humans could have developed much later, as Homo sapiens emerged.
One of the most striking aspects of this study is its innovative approach to understanding the evolution of the human body. In previous studies, researchers had focused primarily on Homo erectus‘s legs and pelvis to assess its ability to walk and run. These studies had largely ignored the important role of the ribcage in endurance activities. However, with the advancement of imaging and 3D reconstruction techniques, the new study was able to build a virtual model of the Turkana Boy’s ribcage, allowing the researchers to simulate how the ribcage would have moved during breathing and how that movement might have affected the individual’s ability to run long distances.
The three-dimensional model created for this study enabled scientists to predict what the Turkana Boy’s ribcage would have looked like had he fully grown into adulthood. The reconstructed ribcage was then compared with the ribcages of modern humans and Neandertals to observe the differences in shape. This comparison revealed that Homo erectus’s ribcage was much wider and more voluminous than that of modern humans, and it resembled the ribcage of other stockier human ancestors, such as the Neandertals. The deeper, broader chest of Homo erectus would have allowed it to take in more air with each breath, which may have been an adaptation for short bursts of activity, rather than sustained endurance running.
This finding has significant implications for how we understand the evolution of human body types. Homo sapiens, with its taller and more slender build, is uniquely adapted for long-distance running and other endurance activities, a trait that is critical for survival in certain environments. In contrast, the stockier build of Homo erectus may have been better suited to other physical activities, such as climbing or more intermittent forms of movement, rather than continuous, long-distance running. The shift towards the modern human body shape, with its focus on endurance and efficient breathing, likely occurred after the time of Homo erectus—possibly around the time that Homo sapiens emerged.
The findings also suggest that Neandertals, another key ancestor of modern humans, may have inherited this stockier ribcage shape from Homo erectus, given the anatomical similarities between the two species. While Neandertals are often depicted as having a robust, muscular build adapted for cold climates, the connection between Homo erectus and Neandertals in terms of body shape further complicates our understanding of human evolution. The different body types of these ancestors reflect a complex history of adaptation to varying environments, with different species emphasizing different physical attributes depending on their ecological needs.
The Turkana Boy fossil, with its detailed skeletal structure, continues to provide valuable insights into the evolutionary history of humans. The new virtual reconstruction of his ribcage allows scientists to examine this critical aspect of Homo erectus‘s anatomy in a way that was not previously possible. It demonstrates the value of cutting-edge imaging technologies in reconstructing ancient anatomies and opens new doors to understanding the physical evolution of human ancestors.
As the field of paleoanthropology continues to evolve, the work of Bastir, García-Martínez, Williams, and others serves as a reminder of how much we still have to learn about our ancient relatives. While Homo erectus has long been considered a key figure in the story of human evolution, the discovery of its stockier build challenges many of our assumptions and invites further exploration into how human bodies evolved over millions of years. This new understanding of Homo erectus emphasizes that the journey from our ancient ancestors to modern humans is far more complex and gradual than we might have imagined.
The evolution of the modern human body is a fascinating story of adaptation to a changing environment. From the stockier, more robust build of Homo erectus to the taller, leaner physique of modern humans, the transformation of the human body reflects not only physical changes but also the evolution of our behavior, our environment, and our survival strategies. Understanding these changes is key to understanding who we are today and how we came to be. The new findings on Homo erectus show us that, as scientists continue to piece together the puzzle of human evolution, there is still much to learn about the deep past of our species and the remarkable journey that led us to where we are now.
More information: Markus Bastir et al. Rib cage anatomy in Homo erectus suggests a recent evolutionary origin of modern human body shape, Nature Ecology & Evolution (2020). DOI: 10.1038/s41559-020-1240-4