Retired Faculty Member of Çukurova University, Medical School, Department of Physiology, Adana, Turkey

A new syndrome characterized by three main symptoms including habitual quadrupedal locomotion, dysarthric or no speech and impaired intelligence with no conscious experience was first described in 2005, called "Üner Tan Syndrome" or UTS. Since then, nine more families were found by the discoverer in various regions of Turkey. My objective is to review and interpret the Üner Tan Syndrome with history, clinical evaluations, genetics, and the dynamics of human quadrupedalism with regard to its self-organized emergent properties.

The cases exhibiting the Üner Tan syndrome were subjected to neurological examinations by one or two experienced neurologists, and blood samples were taken for genetic analysis. Sagittal and coronal MRI scans were performed to visualize the cerebro-cerebellar changes, and videos were recorded to analyze their locomotion. All of the cases exhibited habitual diagonal-sequence quadrupedal locomotion, mild to severe mental retardation without conscious experience, dysarthric or no speech with only a few sounds. In all of the affected cases, dynamic balance was impaired during upright walking, exhibiting truncal ataxia. MRI scans showed inferior cerebellar hypoplasia with mildly simplified cerebral gyri, except one case exhibiting normal brain MRI. All families showed consanguineous marriages in their pedigrees, suggesting autosomal recessive transmission. UTS was genetically heterogenous. It was suggested that the emergence of human quadrupedalism may not be explained by a single factor. Instead, the attractor, human quadrupedalism, as an adaptive self-organized motor behavior, may result from the dynamic interactions of many subsystems, such as the spinal central pattern generators, posture, balance, body constraints, muscle strength, extensor and flexor systems, perception, cognition, motivation, genetics, and the environmental constraints, not depending upon the prior existence of any genetic code or instructions embedded within the central nervous system.