Unertan syndrome: a new variant of Unertan syndrome: running on all fours in two upright-walking children.

A new variant of Unertan Syndrome (UTS) is described in two Turkish children who exhibit both bipedal and quadrupedal locomotion and have normal cognitive abilities, including speech and intelligence. Quadrupedal locomotion was used by these individuals for rapid motivity when needed. An X-linked autosomal recessive transmission appears to be responsible for the UTS trait, with no intrafamilial marriages. The children did not show any neurological signs and symptoms except for a positive Babinski sign and an inability to perform a tandem walk. The results suggest that quadrupedality may result from using ancestral neural networks when needed. The preference for the quadrupedal gait as a hidden skill may be an example of learned dynamical adaptation to limited motor control, pointing out a phase transition in system dynamical terms. Human quadrupedality may have important consequences regarding human evolution with respect to the transition from quadrupedalism to bipedalism, which is generally recognized as important trait in the hominization process during human evolution.