Neandertal knees: power lifters in the Pleistocene?

It has been proposed (Trinkaus, 1983a; Miller & Gross, 1998) that the marke d thickness of Neandertal patellae and/or the posterior displacement of the ir tibial condyles increased their relative M quadriceps femoris moment arm s, thereby making their legs powerful in extension. However, it is necessar y to compare these reflections of muscle moment arm length to appropriate m easures of the body weight moment arm and body mass estimates, both of whic h are influenced by ecogeographically determined body proportions. Reassess ment of tibial condylar displacement and patellar thickness, as well as pat ellar 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 ex ceptionally powerful knee extension. Relative tibial condylar displacement remains above that of a modem industrial society sample, but similar to tha t of the Broken Hill tibia, Late Pleistocene early modern humans and a rece nt human nonindustrial sample. Relative patellar thickness is similar to th at of early modern humans, who have relatively thick patellae compared to t he late Holocene human samples. Consequently, once body proportions are tak en into account, there is little difference between the Neandertals and oth er 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. (C) 1999 Academic Pres s.