A Shared Starting Line
Neandertal infants entered the world at a size remarkably similar to modern humans, yet they quickly diverged in the months that followed. Recent findings published in Royal Society Open Science and Current Biology reveal that while the two species shared comparable body dimensions at birth, Neandertal skeletal development accelerated shortly thereafter.
Reconstructing the German Specimen
The evidence for this parity at birth comes from a late-term fetal or newborn Neandertal skeleton recovered from a German rock shelter. Alvise Barbieri, an archaeologist and geoscientist at the University of Algarve, led a team that employed X-ray imaging to reconstruct 12 fragile bones unearthed from sediment dating back approximately 55,000 years. While the infant’s overall scale mirrored that of a modern human newborn, the physiology told a different story: the arm and leg bones were notably thicker and denser, suggesting a rapid growth trajectory that likely began in the final stages of pregnancy.
The Six-Month Growth Gap
Further clarity emerges from a six-month-old Neandertal infant discovered in a cave in northern Israel. Researchers digitally reconstructed these remains, dated to between 51,000 and 56,000 years ago, to map their maturation against modern benchmarks. While the infant’s teeth aligned with Homo sapiens developmental markers, the limb bones did not. According to paleobiologist Ella Been of Ono Academic College, the arm and leg bones of this six-month-old were comparable in size to those of a modern human roughly twice its age. The data confirms that Neandertals did not follow the same postnatal growth curve as our own species.
Summary of Developmental Divergence
- Birth Size: Neandertal newborns were physically similar in size to Homo sapiens infants.
- Bone Density: Newborn Neandertal arm and leg bones were thicker and denser than those of modern human counterparts.
- Growth Pace: By six months of age, Neandertal limb bones showed development levels typically seen in year-old modern humans.
- Developmental Timing: The accelerated growth rate likely began in utero and became most pronounced during the first years of life.