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UNERTAN SYNDROME
The Unertan Syndrome (UTS), first discovered by Tan in 2005 (see Tan, 2005a) is characterized by three main symptoms: 1) habitual walking on all four extremities, 2) rudimentary intelligence with no conscious experience, and 3) primitive language. Tan discovered nine families with 15 individuals exhibiting UTS.

Hitherto nine families were discovered: all them are resident in the southern Turkey except one who lives in the northern Turkey (Canakkale). The first discovered family lives in Demirkonak (Iskenderun), and has 19 children which are now 15 to 37 years of age, and five of them exhibit the UTS. The father and mother are relatives. The pedigree analysis suggests an autosomal recessive transmission (see Tan, 2005a, b; Tan, 2006a). A second and third families were then discovered in Adana (see Tan, 2006b, c). These families are relatives, and there are two individuals with UTS in Adana families. Although there is no intrafamilial marriage, the pedigree analysis suggested an autosomal recessive transmission in these families, too. A very large family is then discovered in a Eskikonak (Gaziantep). There are six subfamilies within this large family, with intrafamilal marriages, and six individuals exhibiting the UTS. These families also demonstrate autosomal recessive transmission (see Tan et al., 2007, in press). Recently, Tan discovered a new series of families with individuals exhibiting UTS, in a rural area of Canakkale in northern Turkey (see Tan, 2007, in press). The affected individuals in Canakkale family suggested an autosomal recessive transmission with but no intra-familial marriages. In all of these families, there are also bipedal ataxic individuals. The MRI scans showed a cerebellar and vermial hypoplasias in the affected individuals, except that in Adana Family, who showed only a mild vermial hypoplasia in the brain MRI scans. These results suggests that the main symptoms of the UTS may be caused by a vermial hypoplasia as a result of a chromosomal anomaly due to the autosomal recessive transmission. We have found that the chromosome 17p was affected in the first family resident in Demirkonak (unpublished results from a collaboration with Tayfun Ozcelik in Bilkent University. Our collaborative studies showed that the affected individuals from other families have anomalies in different chromosomes (unpublished observations).

Walking style in UTS
The main characteristic of the UTS is the quadrupedal gait. Most of the individuals affected with UTS were able to rise from a sitting position and remain in the upright position for a long time. The main difficulty was the initiation of the necessary leg movement to take the first step using a leg. Although the cerebellar vermis is responsible for truncal balance, the lateral balance during walking is different from the simple balance during standing (see Hof et al., 2007). In the individuals with UTS, the truncal balance was normal during standing without any discomfort, but they lost balance if they tried to take a step, transferring the body weight to the opposite leg and stabilizing it in a fully extensor posture. The quadrupedal man from Canakkale family had fully developed UTS, while he had a normal cerebellum on MRI scan. Moreover, there were biped-ataxic individuals with the same MRI pictures. The neural mechanisms of the upright gait are indeed very complex and not completely understood at this time. Concerning the cerebellar system, the neural control of gait is not limited to the cerebellar vermis or erebellar control systems; normal gait movements of the legs are possible with a normal spinal cord without any interference from the supraspinal centres. This can be easily demonstrated when a baby is held upright with the feet just touching the ground. In this situation the baby begins to move its legs as if stepping, while being unable to balance or support itself independently during stepping since the cerebellar and/or vermial systems needed to support the body during walking movements of the legs are not fully developed yet.

Control of the dynamics of asymmetric lateral balance is involved in counteracting perturbations caused by gait movements themselves. Lateral balance during upright gait may be referred to as “asymmetric lateral balance” and is instantaneously controlled by the spino-cerebro-cerebellar system in humans. If one compares quadrupedal walking in individuals with UTS with babies who make walking movements when held in the upright position, it can be concluded that the spinal walking movements with legs normally occur in individuals with UTS while walking on all four extremities even though they cannot manage the necessary postural adjustments during upright bipedal gait, thus the problem with asymmetric lateral balance.

Walking on all four extremities
Most of the individuals with UTS fall down if they try to take a step. In contrast, all of them walk on all four extremities with great ease, as if it is their natural gait. They therefore likely have a preference for the quadrupedal gait, similar to the psychological variable, hand preference. That is, a right-handed man can write using the right hand with great ease, contrary to the left hand which is very clumsy in writing. Therefore he may prefer his right hand in writing, and vice versa in a left-handed person. Although preference is a psychologic manifestation, it has neural mechanisms to facilitate the right-hand actions in skilled movements. Accordingly, a preference for the qudrupedal gait should have neural mechanisms, too. Walking on all four extremities (bear crawling) is quite normal in some children before upright walking. Children walking on all four extremities were described thoroughly as early as 1928 by Hrdlicka, who reported 11 children walking on all four extremities for about eight months and then standing up and starting to walk bipedally (see Hrdlicka, 1928). Thus, there may be a transitory period during child development on which bear crawling is exhibited. However, as seen in UTS, some children may prefer bear crawling for the rest of their life and continue to walk on all four extremities.

The individuals with UTS preferred quadrupedal walking because of the impossibility or great difficulty in performing upright walking, they would do it also with great difficulty, as can be experienced if tried by anyone. As mentioned above, the preference should have neural mechanisms whether it be a hand preference or walking preference. However, we really do not know the neural mechanisms involved in qaudrupedal walking in apes and humans exhibiting UTS. Apparently, the human quadrupedal gait seen in adults with UTS is a developmental throwback. That is, during the normal development of a child, probably following the evolutionary plan in the child’s genes, may habe stopped at a point of transition from quadrupedality to bipedality. To be able to progress from a quadrupedal gait, a relatively older walking style into a newer walking style such as bipedal locomotion, the evolutionarily newer cerebro-cerebellar systems regulating asymmetric lateral balance for upright walking should be developed in children. If not, these children would remain at the older evolutionary stage of a quadrupedal gait, finding it quite easy, i.e., natural, to walk on all four extremities, as was habitually done by our ancestors. Unfortunately, we do not know the location and functioning mechanisms of the newer cerebro-cerebellar systems responsible for the dynamics of asymmetric lateral balance which is necessary for an upright bipedal gait.

Cognitive faculties
The intelligent actions were in a rudimentary level in the individuals with UTS. They could not answer a single question from the Mini-Mental State Examination Test for uneducated Turkish people. This test attempts to measure the patients capabilities in five fields: orientation (date and location), registration (immediate recall of three words), attention and calculation (count backwards), recall (recall three items), and language and drawing (name a few items, repeat a sentence, paper folding, draw a watch). The patients always had zero scoes in this test, except one who had 2 points from a total of 30 points. Concerning the language, the individuals with UTS from the first family used a language with very limited vocabulary, the others from the remaining families could not speak at all, using only a few sounds to express their everyday wishes.

It is known that cerebellum is involved in cognition except balance and coordination during locomotion. MRI scans revealed that there was a mild cerebral cortical atrophy in except a cerebellar and/or vermial hypoplasia in individuals with UTS. This is associated with the cerebellar cognitive affective syndrome (see Schmahmann & Sherman, 1998), accentuating the interconnections between the cerebellum, cerebral association areas, and paralimbic regions. The severe mental impairments observed in individuals with UTS may be accounted for by the disruption of the cerebro-cerebellar circuits involved in cognition. These patients could in fact understand simple questions and commands, while they had difficulties in expressive language, usually answering questions with unintelligible sound. This also may be a result of a defect in the cerebro-cerebellar circuits involved in language, since the cerebellum has reciprocal connections with the left inferior frontal gyrus and the left lateral temporal cortex (Booth et al., 2007). The role of cerebellum in speech production has been reported frequently. Namely, cerebellar lesions may alter verbal expression and produce slow, monotonus speech that is not understandable (Fabbro et al., 2000).

UTS vs ancestoral traits
Interestingly enough, the individuals with UTS exhibited ancestral features, such as walking on all four extremities coupled with primitive language and rudimentary intelligence. Most of them had no language skills whatsoever, answering simple questions with a simple sound. Finding the gene or genes responsible for these uncestral traits may illuminate the mechanisms, for instance, for the transition from our quadrupedal ancestors to our bipedal ancestors. Studying the fossil records have not been successful in this respect. Indeed, we now have live models to study the human evolution, especially with regard to the much discussed transition from habitual quadrupedality to habitual bipedality associated with mental development. Herein, there has been no intent to insult or injure these individuals affected by UTS, rather this is an endeavor to better understand the mystery of human evolution.

UTS vs devolution
UTS cases are also interesting with respect to devolution, which is manifest in individuals with UTS as an experiment of nature. The term of devolution, originally used by Tan (see Tan, 2005b; Tan, 2006a), was preferred with respect to the evolutionary direction of human beings. So it merely means a reappearance of an earlier trait, such as the reappearance of the habitual quadrupedal gait in individuals exhibiting UTS. That is, as a result of nature’s experiment, UTS with ancestral features appeared in these individuals. The UTS cases are the first examples of devolution in humans. An evolution in reverse or reverse evolution was previously used in some animal studies, as a synonym of devolution (see Porter & Crandal, 2003; Teotonio & Rose, 2000, 2001; Trvdik & Capecchi, 2006). According to ScienCentralNews (08.31.06), Capecchi said that “we are trying to reconstruct what happened during the normal evolutionary process.” Similarly, by studying humans with devolution in UTS exhibiting our most important ancestral trait, such as the habitual qaudrupedal gait, wwe can understand the mechanisms for the transition from habitual qaudrupedality to habitual bipedality, which most likely occurred by punctuated evolution (Elena et al., 1996) resulting from a genetic mutation, provided that we can determine the location of the gene or the gene pool responsible for the quadrupedal gait in humans with UTS. This is apparently contrary to Darwin’s theory of gradual evolution. If the Darwin’s theory of gradual evolution would be correct, all of the monkeys would have started to walk bipedally long ago, at least imitating man.

To elucidate the genetic mechanisms of the transition from quadrupedality to bipedality in human beings would be a groundbreaking scientific development in human history. Therefore, there is no reason to be insulted or suggest injury by the “Unertan Syndrome”.