Limb proportions and the ontogeny of quadrupedal walking in infant baboons (Papio cynocephalus)

Abstract

AbstractMuch of the diversity in preferred walking gait (footfall sequence, interlimb timing) observed among mammals can be understood as a biomechanical response to variation in body shape, in conjunction with efforts to maintain stability. Primates, unlike most other mammals, exhibit a preference for diagonal sequence, diagonal couplets (DSDC) walking gait, but there remains no clear consensus on this gait's possible biomechanical or adaptive advantages. This study examines primate gait from an ontogenetic perspective, and tests the hypothesis that ontogenetic gait transitions are influenced by changes in body shape. Support for this hypothesis could provide insight on the biomechanics and evolution of DSDC gait preferences in adult primates. Data on limb proportions, footfall sequence and interlimb timing were collected at 2‐week intervals for four infant baboons (Papio cynocephalus) as they aged from 1 to 9 months. Despite some variation among individuals, DSDC walking was the most frequently used gait throughout the developmental period, but it was nearly always used in combination with lateral sequence walking. An important transition occurred at c. 5 months, when limb couplets used in lateral sequence walking shifted from diagonal to lateral, and the frequency of DSDC walking increased. The couplets shift within lateral sequence walking coincided with a relative increase in hind limb length, and was most likely attributable to the avoidance of ipsilateral limb interference. Limb proportions thus appear to have a functional influence on lateral sequence walking, but do not explain the consistent use of DSDC walking during the sampled developmental period.