3D‐kinematics of vertical climbing in hominoids

Abstract

Vertical climbing has played an important role in theories about the evolution of habitual bipedalism in early hominids and of locomotor specialization in hominoids. However, empirical data on vertical climbing in nonhuman primates are scarce, especially regarding kinematics. In this paper, the kinematics of flexed-elbow vertical climbing of four hominoid species are reported: western lowland gorillas (Gorilla gorilla gorilla), bonobos (Pan paniscus), Sumatran orangutans (Pongo pygmaeus abelii), and yellow-cheeked crested gibbons (Hylobates concolor gabriellae). The climbing sequences were recorded simultaneously by four digital video cameras in European zoos. Analyzed parameters include intersegmental flexion/extension angles of the shoulder, elbow, hip, and knee joints, horizontal abduction/adduction angles of the upper arm and thigh, and distance of the body center of gravity from the substrate. Analyses reveal that differences in climbing kinematics between individuals of different age/sex classes of one species are mostly size-related, whereas interspecific differences reflect specific locomotor adaptations. The climbing kinematics of bonobos and gorillas are more similar to each other than to those of orangutans or gibbons. The range of motion of the major limb joints in adult orangutans is larger than in African apes, although the hip is not more extended. Gibbons horizontally abduct the arm more and the thigh less during climbing than any of the great apes. These results allow us to question some qualitative descriptions of vertical climbing kinematics reported in the literature, and to discuss implications for the evolution of locomotor adaptations in hominoids.

Functional Anatomy and Adaptation of Male Gorillas (Gorilla gorilla gorilla) With Comparison to Male Orangutans (Pongo pygmaeus)

“…At the hip, the gorilla acetabulum is deepest among the apes (Schultz, 1963a). This anatomical configuration is reflected in behavior, confirmed by observations on locomotion of captive males (Isler, 2005).…”

“…Bone at the hip joint is also less restrictive as reflected in the shallow acetabulum and reduced greater trochanter. The lack of a ligamentum teres (connecting the femoral head and acetabulum) and on average, heavy hip rotators, combine to permit hip circumduction and elevation of the hind limb far above the hip in contrast with gorillas (Isler, 2005). During dissection, we noted the gluteal muscles divide easily; the gluteus maximus has a superior portion on the posterior ilium, and a distinctly separate portion on the ischial tuberosity (ischiofemoralis), whereas, these two portions are continuous in gorillas (Sigmon, 1974;Stern and Susman, 1981).…”

“…On live captive gorillas and orangutans, direct measures of muscle function or joint motion derive from electromyography during specific limb movements (e.g., Basmajian, 1974a, b, 1978;Tuttle et al, 1975;Stern and Susman, 1981;Tuttle et al, 1983) and from cinematography of climbing modes (e.g., Isler and Thorpe, 2003;Isler, 2005).…”

Functional morphology of the ankle and the likelihood of climbing in early hominins

“…Because the force of gravity and the mass of the animal cannot be altered during climbing, reducing the horizontal distance that the animal is from the tree will reduce the torque and thus reduce the muscular forces counteracting gravity, thereby ensuring a safer vertical ascent. This strategy of being close to the vertical substrate during climbing has been theoretically discussed (33)(34)(35)(36) and has been actually observed in animals ranging from geckos (37) to the great apes (38,39).…”

“…Flexion at the hip and knee has been discussed as a means to keep climbing apes close to the substrate (38,39), although these are the first data demonstrating a similar strategy for the ankle.…”