Neandertal knees: power lifters in the Pleistocene?

It has been proposed (Trinkaus, 1983 a; Miller & Gross, 1998) that the marked thickness of Neandertal patellae and/or the posterior displacement of their tibial condyles increased their relative M. quadriceps femoris moment arms, thereby making their legs powerful in extension. However, it is necessary to compare these reflections of muscle moment arm length to appropriate measures of the body weight moment arm and body mass estimates, both of which are influenced by ecogeographically determined body proportions. Reassessment of tibial condylar displacement and patellar thickness, as well as patellar height, relative to an appropriate measure of the moment arm for the baseline load on the knee (body weight), to that moment arm times estimated body mass, and to that moment arm times a skeletal reflection of body mass (femoral head diameter) rejects the hypothesis that the Neandertals had exceptionally powerful knee extension. Relative tibial condylar displacement remains above that of a modern industrial society sample, but similar to that of the Broken Hill tibia, Late Pleistocene early modern humans and a recent human nonindustrial sample. Relative patellar thickness is similar to that of early modern humans, who have relatively thick patellae compared to the late Holocene human samples. Consequently, once body proportions are taken into account, there is little difference between the Neandertals and other later Pleistocene humans in knee extensor mechanical advantage, and all of these fossil hominids are similar in the more important proximal tibial proportions to those of nonindustrial recent humans.