The influence of load carrying on gait parameters in humans and apes: implications for the evolution of human bipedalism

We provide a comparison of loaded and unloaded carrying gait parameters in humans, common chimpanzees (Pan troglodytes), bonobos (Pan paniscus), Western lowland gorillas (Gorilla gorilla gorilla), and Bornean and Sumatran orang-utans (Pongo pygmaeus and Pongo abelii). We consider whether freeing the hands to carry loads could have been a precursor to the evolution of bipedal walking in humans. We attempt to bridge the gap between in situ and ex situ research by collecting data from three locations: the field, the laboratory, and zoos. We use the results of the field work to design the laboratory experiments and then consider the results from the laboratory and zoo together. We observed infant carrying preferences in humans under field conditions and measured gait parameters during loaded and unloaded walking in humans in the laboratory. The results showed that human males and females prefer carrying infants asymmetrically, and carrying a load has no significant influence on spatiotemporal gait parameters. We measured gait parameters in nonhuman apes during free-ranging loaded and unloaded locomotion in zoos. The results showed that carrying a load had little influence on gait parameters.