The Neanderthals breathed differently

The backbone of the Neandertals was more stable than that of modern humans. Likewise, they had the lower ribs oriented more horizontally, which leads the researchers to suppose that their respiration depended more on the diaphragm than on the case of Homo sapiens, where both the diaphragm and the thoracic cage intervene. To reach these conclusions, they have worked with the fossil remains of the Kebara site (Israel), specifically with the fossil remains of the individual Kebara 2.

To create a virtual thorax model, the researchers relied on both the direct observations of the Kebara skeleton 2, currently held at Tel Aviv University, as well as on scanners (computerized axial tomography) of the vertebrae, ribs and pelvic bones. Once all the anatomical elements were gathered, the virtual reconstruction was done by means of a 3D software specifically designed for this purpose. "This was meticulous work," says Alon Barash of Bar Ilan University in Israel, "we had to scan each of the vertebrae and all the fragments of ribs and then re-position them virtually in 3D."

"In the process of reconstruction, it was necessary to 'cut' and realign in a virtual way some bones that showed deformation, as well as to make mirror images of the ribs better preserved to replace those that are worse preserved on the other side," says Gómez-Olivencia.

"The differences between a Neanderthal thorax and a modern human are striking. In the Neandertals, the position of the vertebral column with respect to the ribs indicates a more stable spine. In addition, the thorax is wider in its lower part ", comment Daniel García Martínez and Markus Bastir, researchers from the National Museum of Natural Sciences (MNCN-CSIC) co-authors of the work.

"A broader thorax on its lower part and ribs oriented more horizontally, as can be seen in the reconstruction, suggest that the Neanderthals' breathing was more dependent on the diaphragm," says Been. "Our species depends on both the diaphragm and the expansion of the rib cage. In this study we can see how the use of new technologies and methodologies in the study of fossil remains provide new information to understand extinct species, "adds Mikel Arlegi (UPV / EHU-University of Bordeaux).

These new results are consistent with a recent work by two of the co-authors, Bastir and García-Martínez, in which they support the presence of a greater pulmonary capacity for Neanderthals.

Patricia Kramer of the University of Washington summarizes: "This is the culmination of 15 years of research in the Neanderthal thorax, and we hope that future genetic analyzes will give us additional clues about their respiratory physiology."

The Neanderthals were hunter-gatherers who inhabited western Eurasia for more than 200 thousand years, during both glacial and interglacial periods until they became extinct about 40 thousand years ago. While some of the anatomical regions of these extinct humans are relatively well known, others such as the spine and ribs are less well known because these elements are more fragile and do not conserve well in the fossil record.

In 1983, a partial Neanderthal skeleton (officially called Kebara 2, and nicknamed Moses) belonging to a young male individual who died about 60,000 years ago, was discovered at the Kebara site (Mount Carmel, Israel). This skeleton does not conserve the skull, since time after the burial the skull was removed, probably as a consequence of a funerary ritual. Instead, it preserves all the vertebrae and ribs, as well as other fragile anatomical regions such as the pelvis or the hyoid bone (a bone located in the neck where some of the muscles of the tongue are inserted). It is therefore the skeleton that, up to now, conserves the most complete thorax of the Neanderthal fossil record.

For more than 150 years, Neanderthal remains have been recovered in many places in Europe and Western Asia (including the Middle East), and the shape of the thorax of this human species has been the subject of debate since 1856, when the first ribs belonging to this species were found. human group. In the last decade, virtual reconstructions have become a new tool, increasingly used in the study of fossils.

This methodology is especially useful with fragile fossil remains such as the vertebrae and ribs that make up the thorax. Almost two years ago, the same research team presented a reconstruction of the spine of this same individual, which indicated the presence of a column with less accentuated curvatures in these humans with respect to Homo sapiens.