The aim of this study was to describe additional patients (n = 3) exhibiting the Unertan syndrome (UTS), resident in rural areas of Canakkale. The 8th and 9th families with the UTS, with a total of 16 members affected, have not been previously characterized. A single, non-familial case (Bayramic, Canakkale) occurred during early childhood after an infection with a high fever. Three cases of familial UTS were located in another village in Canakkale. All cases exhibited the three key symptoms of the UTS: (1) walking on all four extremities, (2) primitive language (only sounds), and (3) rudimentary intelligence. Magnetic resonance imaging showed mild vermial hypoplasia in the non-familial case, while there was cerebellar and vermial hypoplasia with a flattened cerebral cortex in the familial cases. Dexterity of the fingers was normal. The man from the latter family was fond of dragging a wooden box after fastening a string around his belt. The collective observations and clinical findings suggest two etiologies for the UTS: (1) genetic, via autosomal recessive transmission and (2) viral, likely the poliovirus affecting the cerebrocerebellar structures. At a minimum, vermial hypoplasia is suggested to cause fully developed UTS. The subjects could stand upright and even walk bipedalty, despite difficulties in balance (ataxia), but they preferred quadrupedal walking. The main difficulty with gait was maintaining a dynamic-asymmetric lateral balance and initiation of the first step during standing. Apparently, a quadrupedal gait in an adult is a developmental regression with absence of the higher control mechanisms for asymmetric lateral balance during bipedal walking. It is suggested that these individuals exhibit ancestral traits; the quadrupedal gait with rudimentary intelligence and primitive speech resulting from viral infections and/or genetic damage may cause devolution (reverse evolution), a manifestation of an experiment of nature as welt as experimental studies in animal models. The results support the notion of punctuated evolution, in contrast to Darwin's theory of graded evolution. Dragging a wooden box using a string wrapped around the belt may also be an example of reverse evolution with regard to tool making, illuminating the very long-lasting period before the invention of the wheel. Herein, there has been no intent to insult or injure these individuals affected by the UTS; rather, this is an endeavor to better understand the mystery of human evolution. Go to the publisher's online edition of International Journal of Neuroscience for the following free supplemental resource: video clips.