An international team of scientists led by Dr. Ella Been, a researcher at Ono Academic College, has completed the first 3D virtual reconstruction of the ribcage of the most complete Neanderthal skeleton unearthed to date, shedding new light on how this ancient human moved and breathed.
The team, which included researchers from universities in Israel, Spain, and the United States, focused on the thorax, the area of the body containing the rib cage and upper spine, which forms a cavity to house the heart and lungs. Using CT scans of fossils from a 60,000-year-old male skeleton known as “Kebara 2” that was discovered in Israel in 1983, the researchers were able to create a 3D model of the chest that is different from the longstanding image of the barrel-chested, hunched-over “caveman.”
The study, which was published in the October 30, 2018 edition of Nature Communications, shows that, contrary to popular belief, Neanderthals had upright posture and spines that were straighter than those of modern humans.
“The shape of the thorax is key to understanding how Neanderthals moved in their environment because it informs us about their breathing and balance,” said Dr. Been, the study’s senior author. “Neanderthals are closely related to us with complex cultural adaptations much like those of modern humans, but their physical form is different from us in important ways. Understanding their adaptations allows us to understand our own evolutionary path better.”
Neanderthals are a type of human that emerged about 400,000 years ago, living mostly from what is today Western Europe to Central Asia. They were hunter-gatherers who, in some areas, lived in caves and weathered several glacial periods before going extinct about 30,000 years ago. Studies in recent years have suggested that Neanderthals and early Homo sapiens interbred, because evidence of Neanderthal DNA has turned up in many populations.
Over the past 150 years, Neanderthal remains have been found at many sites in Europe, Asia and the Middle East. Dr. Been’s team worked with a skeleton labeled Kebara 2 – also named “Moshe” after well-known Israeli archeologist Moshe Shtekelis, who discovered the Kebara Cave in Northern Israel’s Carmel mountain range in 1983. Though the cranium is missing, the remains of the young adult male are considered one of the most complete Neanderthal skeleton ever found. Two different forms of dating of the surrounding soil, thermoluminescence and electron spin resonance, put the age at somewhere between 59,000 and 64,000 years.
Discoveries and studies of other Neanderthal remains in the 19th and early 20th centuries gave rise to theories and images of a stereotypical, hunched-over caveman. Over time, further research clarified scientific understanding of many Neanderthal traits, but some debate has lingered over the structure of the thorax, the capacity of the lungs and what conditions Neanderthals might have been able to adapt to, or not.
Nearly two years ago, Dr. Been’s research team created a virtual reconstruction of the Kebara 2 spine, the first step in updating theories of Neanderthal biomechanics. For this model of the thorax, the researchers used both direct observations of the Kebara 2 skeleton, currently housed at Tel Aviv University, and medical CT scans of vertebrae, ribs and pelvic bones, along with 3D software designed for scientific use.
“Reconstructing the thorax was an exercise in starting from scratch, deliberately trying to avoid being influenced by past theories of how Neanderthals looked or lived,” explained Alon Barash, a researcher at Bar Ilan University in Israel and one of the leading researchers of the team. “This was meticulous work. We had to CT scan each vertebra and all of the ribs fragments individually and then reassemble them in 3D.”
They then used a technique called geometric morphometric analysis to compare the images of Neanderthal bones with medical scans of bones from present-day adult men. The reconstruction of the thorax, coupled with the team’s earlier finding, shows ribs that connect to the spine in an inward direction, forcing the chest cavity outward, with little of the lumbar curve that is part of the modern human skeletal structure. This shape of the rib cage suggests a larger diaphragm and thus, greater lung capacity.
“The wide lower thorax of Neanderthals and the horizontal orientation of the ribs suggest that Neanderthals relied more on their diaphragm for breathing. Modern humans, on the other hand, rely both on the diaphragm and on the expansion of the rib cage for breathing,” said Dr. Been. “Here we see how new technologies in the study of fossil remains are providing new information to understand extinct species. What that means for how Kebara 2 lived is ripe for further research.”