Neanderthal babies were born with the characteristic barrel-shaped rib cage shape previously identified in adult specimens, according to an analysis of digitally reconstructed rib cages from four Neanderthal infants. The findings suggest that Neanderthals' rib cages were already shorter and deeper than that of modern humans at birth, rather than shifting their shape later in development. While scientists have known that adult Neanderthals were heavier than modern humans, requiring significant differences in skeletal shape, there have been few studies that have compared the earliest postnatal developmental stages of Neanderthals and modern humans, due to a lack of well-preserved fossil remains of Neanderthal children. To investigate whether the shape of this hominid's thorax changed shape between birth and adulthood, Daniel García-Martínez and colleagues scanned and virtually reconstructed ribcages from 4 young Neanderthals estimated to be about 1 to 2 weeks old, less than 4 months old, 1.5 years old, and 2.5 years old. The most complete Neanderthal specimen (the 1.5-year-old) also 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 researchers compared rib cage 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 rib cages, regardless of their age at death. García-Martínez et al. conclude that the bulky Neanderthal ribcage may have been genetically inherited, at least in part, from early Pleistocene ancestors.