An international team of researchers has virtually reconstructed the ribcages of four Neanderthal individuals from birth to around 3 years old and found that most of the skeletal differences between the Neanderthal and modern human ribcage are already largely established at birth, the Neanderthal ribcage being deeper and shorter than that of modern humans.
Reconstruction of a Neanderthal. Image credit: Neanderthal Museum.
“Despite genetic similarities that allowed for admixture between Neanderthals and anatomically modern humans, there is a well-established consensus that Neanderthals showed significant morphological differences when compared to humans,” said Dr. Daniel García-Martínez from the University of Bordeaux, the Spain’s Museo Nacional de Ciencias Naturales, and the Centro Nacional de Investigación sobre la Evolución Humana, and colleagues.
“Some of these differences are inherited traits from their Pleistocene ancestors, while others are present exclusively in Neanderthals.”
“Neanderthals were highly encephalized and heavy-bodied hominins requiring large amounts of energy.”
“It has been proposed that to fulfill these energetic demands, their ribcage had a large estimated total lung capacity and a different shape that included a shorter, slightly deeper, and larger chest, compared to modern humans.”
Virtual reconstruction of the four Neanderthal individuals studied by García-Martínez et al.; bones that are preserved in the original specimen are shown in red, whereas mirror images are shown in blue and statistical estimations in gray. Image credit: García-Martínez et al., doi: 10.1126/sciadv.abb4377.
To identify potential differences with modern humans in ribcage morphology, the researchers used virtual and statistical methods to reconstruct the ribcage of four young Neanderthals.
Specifically, they reconstructed the ribcages of perinatal individuals of Mezmaiskaya 1 (7 to 14 days old) and Le Moustier 2 (less than 120 days) and infant individuals from Dederiyeh 1 (1.41 years) and Roc de Marsal (2.54 years).
The most complete Neanderthal specimen, Dederiyeh 1, revealed the species had relatively longer mid-thoracic ribs compared to its uppermost and lowermost ribs and a spine folded inward toward the center of the body, forming a cavity on the outside of the back.
The scientists compared ribcage development in these specimens with a baseline for modern human development in the first three years of life, which they derived from a forensic assessment of remains from 29 humans.
The Neanderthal specimens had consistently shorter spines and deeper ribcages.
“The bulky Neanderthal ribcage may have been genetically inherited, at least in part, from early Pleistocene ancestors,” the authors concluded.
Their paper was published in the journal Science Advances.
_____
Daniel García-Martínez et al. 2020. Early development of the Neanderthal ribcage reveals a different body shape at birth compared to modern humans. Science Advances 6 (41): eabb4377; doi: 10.1126/sciadv.abb4377
