Walking on all Four limbs. The quad walkers. Uner Tan syndrome.

I wrote a multipart series on Uner Tan Syndrome, the people who walk on all fours years ago. Recently there has been a video of a young lady walking and running on all 4 limbs, like some kind of cat or canine. It triggered me to put this article up again on the research and thoughts behind this quadruped gait in humans. It worth rewinding today. We have written and updated several of our, and Dr. Tan's, theories and thoughts on it from direct communication with Dr. Tan. You can search for all the parts under "uner tan" in the search box.

"From the viewpoint of dynamic systems theory, it was concluded there may not be a single factor that predetermines human quadrupedalism in Uner Tan syndrome, but that it may involve self-organization, brain plasticity, and rewiring, from the many decentralized and local interactions among neuronal, genetic, and environmental subsystems."

Full Blog post here:


The hand walkers: The family that walks on all fours. Part 1

Quadrupedalism and its commentary on human gait. To understand your athlete, your patient, your client, whatever your profession, you need to have a good understanding of neurodevelopment. If your client has some functional movement pattern flaws it could be from a delayed or expedited neurodevelopmental window. Generalized training and rehab will not correct an early or late window issue; often your work must be more specific.

When we began our journey into our daily writings on “The Gait Guys blog” we had no idea of the never ending tangents our writing would take pertaining to gait, human movement and locomotion. It has become plainly obvious over time that this blog will likely exist as long as we choose to continue it.

In 2006 we saw a documentary documentary entitled The Family That Walks On All Fours LINK: https://www.youtube.com/watch?v=ef3eKj4Pivk&feature=youtu.be
. . . and the video clip is from the documentary. It was a fascinating documentary and with our backgrounds in neurology, neurobiology, neuroscience, biomechanics and orthopedics we had more questions than the documentary touched upon. The documentary opened up many thoughts of neuro-development since we all start with a quadrupedal gait. But there had to be more to it than just this aspect because people eventually move through that neurologic window of development into bipedial gait. This has been in the back of our minds for many years now. Today we will touch upon this family and their challenges in moving through life, today we talk about Uner Tan syndrome, Unertan syndrome or UTS.

The original story is about the Ulas family of nineteen from rural southern Turkey. Tan described five members as walking with a quadrupedal gait using their feet and the palms of their hands as seen in this video. The affected family members were also severely mentally retarded and displayed very primitive speech and communication. Since his initial discovery several other families from other remote Turkish villages have also been discovered. In all the affected individuals dynamic balance was impaired during upright walking, and they habitually chose walking on all four extremities. Tan proposed that these are symptoms of Uner Tan syndrome.

UTS is a syndrome proposed by the Turkish evolutionary biologist Uner Tan. Persons affected by this syndrome walk with a quadrupedal locomotion and are afflicted with primitive speech, habitual quadrupedalism, impaired intelligence. Tan postulated that this is a plausible example of “backward evolution”. MRI brain scans showed changes in cerebellar development which you should know after a year of our blog reading means that balance and motor programming might be thus impaired. PET scans showed a decreased glucose metabolic activity in the cerebellum, vermis and, to a lesser extent the cerebral cortex in the majority of the patients. All of the families assessed had consanguineous marriages in their lineage suggesting autosomal recessive transmission. The syndrome was genetically heterogeneous. Since the initial discoveries more cases have been found, and these exhibit facultative quadrupedal locomotion, and in one case, late childhood onset. It has been suggested that the human quadrupedalism may, at least, be a phenotypic example of reverse evolution.

Neurodevelopment of Children:

Children typically go through predictable windows of neurodevelopment. Within a set time frame they should move from supine to rolling over. Then from prone they should learn to press up into a push up type posturing which sets up the spine, core and lower limbs to initiate the leg movements for crawling. Once crawling ensues then eventual standing and cruising follow. In some children, it is rare yet still not neurodevelopmentally abnormal, they move into a “bear crawl” type of locomotion where weight is born on the hands and feet (just as in our video today of UTS). Sometimes this window comes before bipedalism and sometimes afterwards but it should remain a short lived window that is progressed through as bipedalism becomes more skilled.

In studying Uner Tan Syndrome, Nicholas Humphrey, John Skoyles, and Roger Keynes have argued that their gait is due to two rare phenomena coming together.

“First, instead of initially crawling as infants on their knees, they started off learning to move around with a “bear crawl” on their feet.Second, due to their congenital brain impairment, they found balancing on two legs difficult.Because of this, their motor development was channeled into turning their bear crawl into a substitute for bipedalism.”

According to Tan in Open Neurol, 2010

It has been suggested that the human quadrupedalism may, at least, be a phenotypic example of reverse evolution. From the viewpoint of dynamic systems theory, it was concluded there may not be a single factor that predetermines human quadrupedalism in Uner Tan syndrome, but that it may involve self-organization, brain plasticity, and rewiring, from the many decentralized and local interactions among neuronal, genetic, and environmental subsystems.

There is much more we want to talk about on this mysterious syndrome and the tangents and ideas that come from it. We will do so in the coming weeks as we return to this case. We will talk about other aspects of neurodevelopment which should be interesting to you all since most our readers either are having children, will have them, or are watching them move through these neurologic windows. And we know that some of our readers are in the fields of therapy and medicine so this should reignite some thoughts of old and new. In future posts we will talk about cross crawl patterning in the brain, bear crawling, the use of the extensor muscles in upright posture and gait as well as other aspects of neurodevelopment gone wrong. We are not even close to being done with this video and all of its tangents. In the weeks to come we hope you will remain interested and excited to read more about its deep implications into normal and abnormal human gait.

author: Dr. Shawn Allen, one of the gait guys


Open Neurol J.

2010 Jul 16;4:78-89. Uner tan syndrome: history, clinical evaluations, genetics, and the dynamics of human quadrupedalism.

Tan U

.Department of Physiology, Çukurova University, Medical School, 01330 Adana, Turkey.

link: http://www.ncbi.nlm.nih.gov/pubmed/21258577

Humphrey, N., Keynes, R. & Skoyles, J. R. (2005).

“Hand-walkers: five siblings who never stood up”


Discussion Paper

. London, UK: Centre for Philosophy of Natural and Social Science.






The Cheetah man, PART 2: “Bird Dog”, again.

In last week Wednesday’s blog post (link) we discussed the video of this man running amazingly on all 4 limbs at an incredible speed. He was doing it beautifully, most people would have fallen flat on their face after the first leap forward. 

As we discussed on that day, and these 2 screenshot photos will prove, there is ipsilateral interference between the foot and hand in this quadrupedal gait. This is diagonal quadrupedal locomotion (QL); the forward moving lower limb is impaired from further forward progression by the posting up (contact) hand of the same side.  However, in his case, there is such quick removal of the leading hand/limb that he can advance the ipsilateral foot/leg as far forward as he is able without impediment from the same side hand contact. 

As we mentioned in the Bird Dog post last week, (see photo of lady on yoga mat above) the contralateral upper limb will be in the opposite phase of the contralateral lower limb. ie when the left lower limb is in extension, the right upper limb will be in flexion (this is the classic Bird Dog position).

In last weeks blog post (see photos above), the opposite is clearly happening. One can see in the first photo that bird dog is clearly not helping to train a gait pattern, and that is ok, it has other values at times. Rather, in this first photo we see left hip extension and right shoulder extension, just as we see in the baby photo. This contradicts Bird Dog but this does support bipedal gait patterns.  Think about gait. Your right leg and left arm flex until about midstance, when they start to transition into extension; the left leg and right arm are doing the opposite. At no point are the arm and opposite leg opposing one another as in Bird Dog.

As Ivo would say , “if you look at it neurologically, it is a crossed extensor reflex.  It is very similar to a protective reflex called the “flexor reflex” or “flexor reflex afferent”.

The principles remain intact.

More critical thinking today. Hope you enjoyed.

Shawn and Ivo,

The gait guys