Lower limb entheseal morphology in the Neandertal Krapina population (Croatia, 130,000 BP)

Although the Neandertal locomotor system has been shown to differ from Homo sapiens, characteristics of Neandertal entheses, the skeletal attachments for muscles, tendons, ligaments and joint capsules, have never been specifically investigated. Here, we analyse lower limb entheses of the Krapina Neandertal bones (Croatia, 130,000 BP) with the aim of determining how they compare with modern humans, using a standard developed by our research group for describing modern human entheseal variability. The entheses examined are those of the gluteus maximus, iliopsoas and vastus medialis on the femur, the quadriceps tendon on the patella, and soleus on the tibia. For the entheses showing a different morphological pattern from H. sapiens, we discuss the possibility of recognising genetic versus environmental causes. Our results indicate that only the gluteus maximus enthesis (the gluteal tuberosity), falls out of the modern human range of variation. It displays morphological features that could imply histological differences from modern humans, in particular the presence of fibrocartilage. In both H. sapiens and the Krapina Neandertals, the morphological pattern of this enthesis is the same in adult and immature femurs. These results can be interpreted in light of genetic differences between the two hominins. The possibility of functional adaptations to higher levels of mechanical load during life in the Neandertals seems less likely. The particular morphology and large dimensions of the Krapina enthesis, and perhaps its fibrocartilaginous nature, could have been selected for in association with other pelvic and lower limb characteristics, even if genetic drift cannot be ruled out.