title: Siblings in Kars, Turkey, with Uner Tan syndrome (quadrupedal locomotion, severe mental retardation, and no speech): a novel theory for the evolution of human bipedalism.
abstract: OBJECTIVE
  To investigate siblings from Kars (n  =  2), Turkey, with diagonal-sequence quadrupedal locomotion (QL), severe mental retardation, and no speech (Uner Tan syndrome, UTS), in relation to the evolutionary emergence of human bipedal locomotion (BL).
  
  
  METHODS
  Video recordings were made to assess gaits. Brain MRI scanning was performed to visualize the cerebro-cerebellar malformations. Genome-wide association analyses were performed in venous blood samples.
  
  
  RESULTS
  One of the two men with UTS showed early-onset QL and late-onset BL without infantile hypotonia, the other consistent QL with infantile hypotonia. No homozygosity was found in the genetic analysis. The family lived under extremely poor socioeconomic conditions.
  
  
  CONCLUSIONS
  Low socioeconomic status may be a triggering factor for the epigenetic emergence of UTS. The neural networks responsible for the ancestral diagonal-sequence QL, evolutionarily preserved since about 400 MYA, may be selected during locomotor development, under the influence of self-organizing processes during pre- and postnatal periods. The diagonal-sequence QL induced ipsilateral limb interference in UTS cases as in nonhuman primates. To overcome this condition, our ancestors would prefer the attractor BL. This novel theory for the evolution of human bipedalism was evaluated in light of dynamical systems theory.
authors.forename: Uner
authors.initials: U
authors.lastname: Tan
mesh_terms: D005075:Biological Evolution; D001921:Brain / Q000002:abnormalities; D005684:Gait / Q000235:genetics; D055106:Genome-Wide Association Study; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics*; D008124:Locomotion / Q000235:genetics; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D035781:Siblings / Q000523:psychology*; D012923:Social Class; D013064:Speech Disorders / Q000235:genetics; D013577:Syndrome; D013598:Systems Theory; D014421:Turkey; D014741:Video Recording
keywords: Dynamical systems theory; Evolution,; Quadrupedal,; Speech,; Uner Tan syndrome,