Interaction of central and peripheral factors in the control of human posture and locomotion is a long standing topic. As Sherrington so accurately expresses in the statement “posture follows movement like a shadow,” this highlights the interrelation of posture and movement . Tonogenic circuitry is a component of several, diverse supraspinal structures, including rostral ward, for example, the reticular formation, vestibular nuclei, the cerebellum, and selected mesodiencephalic nuclei. Here the two aspects of the locomotor circuitry functioning will be discussed: importance of muscle tone and development of locomotion in humans. Any reflection on the nature of human bipedalism should include a consideration of the mechanisms determining the choice of unconscious habitual posture. Disturbances in postural tone may also result in the emergence of quadrupedal gait in humans. Human stepping movements emerge in utero and show several milestones during development to independent walking. We examined the development of the spinal motor output by identifying the basic patterns of lumbosacral motoneuron activity from multimuscle recordings and by mapping the distribution of motoneuron activity in the lumbosacral spinal cord in stepping newborns, toddlers, preschoolers and adults. Muscle activity during human locomotion is accounted for by a combination of few basic patterns, each one timed at a different phase of the gait cycle. In particular, the two basic patterns of stepping neonates are retained through development, augmented by two new patterns first revealed in toddlers. The alternating spinal motor output is consistent with a simpler organization of neuronal networks in neonates. The development of human locomotion from the neonate to the adult starts from a rostrocaudal excitability gradient and involves a gradual functional reorganization of the pattern generation circuitry.