(I am republishing a lot of my ‘legacy content’ from our PLOS Neuroanthropology weblog, which has been taken down, along with many of the other founding PLOS Blogs. Some of these, I am putting up because I teach with them. If you have any requests, don’t hesitate to email me at: greg (dot) downey @ mq (dot) edu (dot) au. I suspect many of the links in this piece will be broken, but I will endeavour to try to slowly rebuild this content. Originally published 5 September 2010.)

Beginning in 2005, reports by Prof. Üner Tan of Cukurova University in Turkey alerted the world to a number of families in which some members walked quadrupedally. This is the second part of a (so far) two-part post on Uner Tan Syndrome. Although you’re welcome to read the first part, I’ll give you the one sentence summary if you just want to push on and a piece of video clip on the cases. I should warn you though, before you read the first part, that the whole thing is sort of like the straight set-up for this piece, which is a bit of a googly (kind of like a knuckleballer for all you non-cricket followers):

Üner Tan described four consanguineous Turkish families with fourteen individuals who habitually walked quadrupedally; subsequent genetic research showed that some of the families had defects in a gene known to be essential in cerebellar formation, but not all of the cases had the gene, and at least one family member with the gene walked normally, leading most researchers to argue UTS was genetically heterogeneous in origin; some theorists, including Tan, argued that quadrupedalism was either ‘reverse evolution’ or an atavism, but not everyone was buying that explanation (including me for reasons I didn’t make entirely clear in the first post).

Well, that was — technically — one sentence.

Nova preview: The Family that Walks on All Fours

But if you read that first post, I know what you’re saying: ‘Bloody loooong post, mate, laffed mi head off at the picture… but eef thas what yous blokes do at Newroant-whatevs, well, I’m not heaps intristed.’ (Apparently, you have a bogan Australian accent, at least in my head.)

Photo by Eadweard MuybridgeAu contraire – we’re just getting started! We’ve still got bipedal dogs and goats, kids who only get down on all four when in a hurry, Johnny Eck (aka the ‘Half Boy’), capoeira training in Brazil and some other surprises up our sleeve. We’ll show you how we roll at Neuroanthropology, with lots of weird SFW videos and obscure case studies!

One of the things that we try to bring to ‘neuro-’ to make it truly ‘neuroanthropology’ is a much more open consideration of human variation. This can sometimes take us to some extraordinary case studies, not simply out of a fascination with the exotic, but because a comparative look at extreme cases – like Uner Tan Syndrome – helps us to better understand human potential. So let’s go back to Prof. Tan…

More and more quadrupeds

One of the great things about Prof. Üner Tan is that he was not contented just to have a rare genetic condition named after him. (Which would be pretty cool, so if anyone needs a name for one of these things, mine’s available.) Instead, Prof. Tan seemed to search obsessively for other cases in which people walked quadrupedally.

The diversity of underlying conditions was already a problem for explanation, as I’ve discussed in the previous posting because no single genetic anomaly could be found in all the cases (see also, Tan and Tan 2009: 910). But as the number of cases grew, even though Üner Tan kept referring to them as ‘Uner Tan Syndrome,’ the more it became clear that he was not simple on the trail of a single ‘syndrome.’ Rather, he found a range of people who wound up quadrupedal. Moreover, they had become quadrupedal in different ways and for diverse reasons.

For example, Prof. Tan sent me a pre-print version of a ‘Letter to the Editor’ in the journal, Movement Disorders, describing the case of a 12-year-old boy who, about two years earlier, had begun to run on hands and feet. Unlike the prior cases, this boy was a ‘facultative’ quadruped, only using his arms to get about when in a hurry; like the other cases, the boy demonstrated a range of developmental problems (he didn’t speak) and cerebellar symptoms: ‘limb dysdiachokinesia, dysmetria, past-pointing, excessive rebound, kinetic tremor, trunk titubation, and inability in tandem gait’ (Tan et al. 2010). Unlike the other Uner Tan Syndrome cases who had never learned to walk upright, he could walk bipedally, but then at adolescence became more comfortable moving about quadrupedally in certain circumstances.

Clearly, the 12-year-old had some neurological issues, but unlikely the same degree of defect that produced the profound intellectual and motor deficits in the first four families (which were themselves the product of at least three different abnormalities). Moreover, by adding ‘facultative’ (that is, voluntary) quadrupedalism as a category of Uner Tan Syndrome, Prof. Tan himself was starting to focus much more on a single symptom, not a cluster, and allowing for that ‘symptom’ to be intermittent and voluntary. Don’t get me wrong, I’m in agreement we should consider facultative and habitual quadrupedalism together for theoretical purposes, but I’m not the one with the syndrome named after me, so I don’t have anything at stake if we undermine its credibility qua ‘syndrome.’

Running child with UTS (from Tan & Tan 2009: 913)Two more subsequent cases, children 4- and 8-years-old, also had facultative quadrupedalism, getting about bipedally when walking slowly but switching to all four when moving fast. Tan and Tan (2009) found that the children could even ‘gallop’ when trying to sprint, not just using the diagonal-sequence, alternating gait that was found in the original set of families but bounding with the legs or arms moving in unison. These two children were otherwise normal, with no neurological abnormalities, except for a positive Babinski reflex, a foot response which usually indicates neurological problems, and an inability to balance when ‘tandem walking,’ walking heel-to-toe in a straight line (like a test sometimes given to suspected drunk drivers in the US).

All three of these children didn’t have the other hallmarks of Uner Tan Syndrome found in the first four families: no consanguineous marriages (their grandmothers were sisters), no other intellectual deficits, no abnormality in trunk stability, normal language abilities and coordination (Tan and Tan 2009).

Moreover, Tan also found some cases where the patients had no symptoms other than quadrupedal walking, such as a 36-year-old man in Adana, Turkey, with no cognitive deficits or cerebellar problems who walked quadrupedally, due in large part to a leg paralyzed by childhood polio and his refusal to wear a prosthesis (Tan 2007). Three more similar cases followed of neurologically normal individuals who walked quadrupedally due to polio-induced paralysis of their right legs (what’s with the right leg?; see Tan and Tan 2009: 911).

In other words, Prof. Tan was content to call anyone moving quadrupedally an example of Uner Tan Syndrome, even though the etiology of the condition was clearly different, accompanying subordinate symptoms were wildly different, and the primary diagnostic itself varied from voluntary behaviour to inescapable condition.

Uner Tan even pointed to the work of photographer Eadweard Muybridge, famous for his pioneering versions of moving pictures, in which he documented diverse people in everyday activities. Muybridge photographed an English child with a paralyzed leg who, like the last cluster of subjects examined by Tan, also walked on all four. I found the following short film clip by Keith Phillips on YouTube, based on Muybridge’s photos of the quadrupedal child:

Tan repeatedly argues that these examples all demonstrate ‘reverse evolution’ or the unmasking of an ancient vestigial capacity for quadrupedal movement still hidden in the human nervous system. But, as he has found more and more cases, some with no genetic and minimal neurological abnormalities (except for, say, poliomyelitis), I think that the evidence points to a much more interesting possibility: in some cases, whether due to injury, cerebellar deficit or even something more exotic or elective — like circus or capoeira training — humans can develop in their seemingly unsuitable bodies a remarkable capacity to move about on all four. These human quadrupeds demonstrate how activity patterns can shape our bodies, how even defining traits of our species can be absent or developed in distinctive configurations.

Strange bipeds

The cases of some strange bipeds, however, help to build the circumstantial case against the idea that the quadrupedalism found in the cases of Uner Tan Syndrome is simply an atavism or a form of ‘reverse evolution’. Although these cases do not prove the absence of an ancient, masked ability to move quadrupedally, they do show that novel and evolutionarily unprecedented movement situations can produce some remarkable locomotion techniques that can be explained without any recourse to deeply embedded atavisms.

Johnny Eck, from the Johnny Eck MuseumJohnny Eck, referred to by such stage names as the ‘Half Boy,’ seen here in a pitchcard from 1920, is one case of innovation in locomotion. Eck was born in Baltimore in 1911, one of a pair of twins.

Although his brother, Robert, was normal, Johnny’s body terminated just below his ribs (I have not searched for any report by an anatomist, but general details are available at the Johnny Eck Museum website [http://www.johnnyeckmuseum.com/bio.html]). Eck only measured about eighteen inches tall, yet, despite his unusual anatomy, lived to be 79.

Video clips of Eck as a circus performer show him getting about gracefully by walking on his hands; he scales ladders, balances on a single palm, and demonstrates an extraordinary range of motion, only possible because his body was missing legs. This clip also includes commentators talking about Eck and his role in the movie, Freaks.

Johnny Eck and the movie, Freaks, discussed

Similarly, Paralympic multiple Gold Medalist Kurt Fearnley, an extraordinary wheelchair racer (having

Paralympian Kurt Fearnley on the Kokoda Track.won 28 marathons in his class), is also a remarkable ‘walker,’ finishing the Kokoda Trail in 2009. For Australians, the Kokoda Trail, a 96-kilometre (60-mile) track through the Owen Stanley Range in Papua New Guinea, site of fierce fighting between the Australians and Japanese during World War II. Although the track usually takes around a week to ten days to cover, the difficult climbing made more challenging by heat, humidity, mud and frequent rain, Fearnley completed it in eleven days; unremarkable unless you consider that he did it on his hands as he was born with severely underdeveloped legs. (The video is part 2 of a report on Fearnley’s Kokoda ‘crawl’ but it has the best footage of Fearnley moving, and a short moment when he encounters a disabled Papuan boy with a quite different locomotion technique.)

Eck and Fearnley likely have developed quite different hand-walking gaits, not because an ancient ancestor of theirs once got about in this fashion, but because a dynamic relationship between their bodily potential, gravity, and other constraints, including a need for efficiency, pushed them to refine distinct forms of hand-walking. Fearnley, for example, has a much longer body than Eck had, including his underdeveloped legs themselves with which he must contend. The activity then also affects their physiological development, producing a body that is increasingly well suited for this sort of locomotion, with the necessary muscles and callouses.

One can also find examples of extraordinary bipeds in the animal kingdom, including my favourite, the amazing two-legged goat described in 1942 by Dutch veterinarian E. J. Slijper. After he raised it, when the bipedal goat passed away, Slijper dissected the animal to find a host of anomalies, including even convergent bone remodeling in line with other bipedal animals. The example is used by Mary West-Eberhard (2003) in her magisterial discussion of phenotypic plasticity and evolution to illustrate the way that activity patterns can shape profoundly a range of anatomical structures. [see also a discussion of Slijper’s Goat at Pharangula].

Currently, one can cite the case of Faith, the walking dog. The videos are great, but be aware going into it that Faith’s family don’t exactly take a neuroanthropological approach to Faith’s extraordinary plasticity: they see the dog as a sign from God, a ‘miracle,’ and a source of inspiration. What I find interesting in the Oprah-narrated video about Faith is not the praise offered to this ‘inspirational dog’s’ ‘dogged determination’ and indomitable ‘can do’ spirit, not the blizzard of uplifting clichés, but the family’s training techniques: peanut butter and gummy bears for successful hops, abundant interaction with bipedal humans.

Faith the walking dog, various clips

Both Slijper’s goat and Faith the walking dog developed bipedal locomotion because they were born with severely underdeveloped forelimbs, suggesting that animals with unusual bodily configurations can find similarly unusual forms of locomotion, even when they have no atavistic configuration to fall back on. No one would argue that goats or dogs were ‘reverse evolving’ by learning to walk bipedally, or that Johnny Eck’s or Kurt Fearnley’s arm-bipedalism was an atavistic regress to an ancestral form of legless locomotion.

In addition, these forms of unusual locomotion likely make use of pre-existing neural pathways that subserve other functions, including locomotion, in members of their species that are born with a normal complement of limbs. Being born with unusual limbs does not entail also being born with unprecedented neurological structures.

The point is simply that we don’t have to posit an underlying, primitive motor program for quadrupedal movement in the cases of Uner Tan Syndrome to explain the ability to walk on all four. The conservation of neurological structures, their exaptation for new purposes (the reutilization of features that arose for different purposes earlier in phylogeny), is more common and more logical, especially confronted with unprecedented forms of locomotion.

Expert ‘bear walking’

One of the most interesting things about the quadrupedal movement of the Turkish families, however, is that they’re so good at walking on all four. If we consider their movement, not simply as defective, but as a neurological achievement, their solution to the motor problems caused by abnormalities in the cerebellum is, in fact, exceptional.

Although several papers refer to the Uner Tan Syndrome individuals as ‘wrist walking,’ they actually walk palmigrate by all accounts (stated clearly in Ozcelik et al. 2008). The individuals place their palms or ball of the hand on the ground, sometimes pulling their fingers up so that they do not come into contact with the ground at all, or touch only at the tips. This mode of walking is, of course, different from gorillas and chimpanzees, who walk on their knuckles, and from orangutans, who walk on closed fists (the first joint rather than the second).

As Ozcelik and colleagues (2008: 4235) point out, the chief difference between sufferers of Disequllibrium Syndrome (DES-H), often called the ‘Hutterite families’ in the literature, who also have cerebellum problems, and the patients with Uner Tan Syndrome, is that the UTS individuals get around so well. The hallmark of UTS is specifically the patients’ ‘consistent adoption of efficient quadrupedal locomotion.’ As Ozcelik and collaborators go on to opine:
‘In our view, the movement disorder described for the Hutterite patients may be a more profound deficit, with the patients perhaps lacking the motor skills for quadrupedal locomotion.’

Humphrey, Skoyles and Keynes (2005: 4) offer an elaborate observation of the Turkish UTS sufferers’ gaits, describing how their movement ‘even when climbing or descending steps, is on all fours…. They move in this way fluently and effectively, and seemingly without discomfort.’ Humphrey and colleagues are well aware that this versatile quadrupedalism is itself an extraordinary achievement: ‘This [their fluency and effectiveness] contrasts markedly with normal adult humans who find such a gait – if and when they try it – tiring and uncomfortable even after practice’ (ibid.).

The habitual quadrupedalism leaves their ulnar palm and wrist heavy calloused, but, because the individuals raise their fingers off the ground when walking, the fingers ‘show little extra wear’ and ‘retain considerable dexterity’ (ibid.: 6), especially in light of their other motor problems. Walking on the ball of the hand, they can even carry things in their hands when walking quadrupedally. In addition to the adaptation of the hands, the muscles of the lower back, at least in the adult male UTS sufferer, appear to Humphrey and colleagues to be ‘exceptionally well developed’ (ibid.).

In other words, the constant habitual quadrupedal movement gives Uner Tan Syndrome patients exceptional facility at the movement, including bodily adaptations ‘built by crawling’ to make their bodies capable of feats that most adults would find ‘tiring and uncomfortable,’ at best. In spite of the stigma that they face, Humphrey and his colleagues (2005: 4) describe the remarkable perceptual, motor and muscular abilities that one of the patients possesses:

The local villagers laugh at and tease them. Because of this, the females tend to stay close to the house, but the male sometimes wanders for several kilometres. He helps raise money for his family by collecting cans and bottles, which he carries home in a pouch made from his shirt, held by his teeth. He is remarkably agile. We watched him moving easily across rough terrain in search of collectibles. While he searched ahead, his hands anticipated the contours of the rocks, so that he placed them deftly without looking down. He was able to run ahead of us, carrying his mouth bag – while at the same time, to show off, he kicked one of his legs in the air…

The physical adaptations among the individuals with UTS, like those of Slijper’s goat, or, for that matter, Johnny Eck’s or Kurt Fearnley’s or Faith the Dog’s, may appear to be the direct consequence of a congenital abnormality, but the adaptations are equally the result of compensatory activity. One does not get hardened, calloused palms, exceptionally well-developed back muscles, arms capable of carrying one’s weight, without moving in these ways (or doing some similar activity). Disability does not produce compensatory adaptations; alternative action patterns produce these adaptations.

Similarly, the later UTS patients, those with facultative quadrupedalism, also had physical adaptations that made their form of locomotion surprisingly efficient and dexterous. For example, one of the older men who had suffered poliomyelitis, leaving one leg paralyzed, did not become quadrupedal because he had no other options for mobility:

He had always rejected any prosthesis to help him walk upright. Instead, he preferred wrist-walking, using his hands and the unaffected leg. He was quite strong, running through steps very rapidly. (Tan and Tan 2009: 911)

The adaptations extend into the nervous system itself, such as in the case of a young man who only started exhibiting quadrupedal movement at ten years of age and only when moving quickly. As Meliha Tan and colleagues (forthcoming) describe:

Apparently, the patient’s motor system was prepared during his first 10 years to run economically on all four extremities, and the slow, uneasy, ataxic, upright gait was replaced by rapid, easy, and well balanced quadrupedal gait. That is, it took 10 years for rewiring of his motor system to create a new walking style. This suggests any self-organization within the nervous system may take a long time to establish a novel locomotion.

These adaptations likely appear extraordinary to us — and they are profoundly abnormal from a statistical perspective — but quadrupedal human bodies and exotic bipeds are not more shaped by their activities than ours are. Without ‘normal’ motion, our bodies would not have their ‘normal’ shapes (by the way, ‘normal’ was in scare quotes because, of course, what’s ‘normal’ physical activity to one person may be exotic, unthinkable or outrageous to another). All physiological development is activity dependent, just as it is genetic dependent; a gene doesn’t make a person an adept quadruped, although it may make becoming an adept biped virtually impossible (although the examples of Slijper’s goat and Faith should give us pause).

An odd digression with data I can’t explain

One of the more bizarre observations made in an early article (Tan 2006c: 1545) and not repeated in any other piece, is that the members of the second family with Uner Tan Syndrome had limb proportions more in line with Australopithecenes than with modern Homo sapiens:

Interestingly enough, the ratio of arm length to leg length was found to be 90% for the quadrupedal man, 83% for the bipedal man with ataxia, and 78% for the quadrupedal woman. Human-like apes have a ratio about 90% or slightly more, Lucy’s ratio was estimated to be 85%, and human have a ratio of around 70%…

If this is, in fact, accurate, the situation is more bizarre than I’m suggesting. Prof. Tan sees the limb proportions as further confirmation of ‘reverse evolution’ (although not in the male subject?). I have no explanation for this observation: I’d like to be able to say that it might be an example of phenotypic adaptation, a trait produced by the pattern of use, but I simply don’t think it’s possible to change limb length this way. So if the observation is accurate, I have no idea what’s going on, unless the legs are being shortened relative to the arms by some sort of deformation.

Although there might conceivably be some link between the genetic anomalies that produce cerebellar abnormalities in UTS and limb length, I know of no such link and think it’s improbable, to say the least (might. conceivably. okay, I’m trying. yup, I’m not getting it either…). That’s enough of that digression…

Why aren’t more people quadrupedal?

Türkmen and colleagues (2008: 1073) point out that the achievements of the individuals with UTS, their ability to move quadrupedally, is not a capacity limited to those with UTS:

The family presented here shows us that although the morphological adaptive changes for bipedalism in the skeletal and central nervous systems have been established, efficient quadrupedal locomotion is still possible in humans.

Translation: you’re not quadrupedal because you don’t try hard enough and don’t stick with it very long when you do try. It’s still possible.

But certainly, you might say, walking around on all four might be good, but being on two legs is better, right? Who’d want to walk like the folks with Uner Tan Syndrome?

I have to admit that one reason I’m so interested in ‘bear walking’ is that, when I did my fieldwork in Brazil on Capoeira Angola, I spent a lot of time developing my own quadrupedal movement techniques. Like the individuals examined by Prof. Uner Tan and the other researchers, especially the facultative quadrupeds, we capoeira devotees also found our bodies adapting to the demands of quadrupedal movement.

Capoeira Angola is an Afro-Brazilian danced martial art, and the style that I studied, about which I wrote my first (and, so far, only) book, demanded enormous facility in moving close to the ground. A non-contact martial art in which the practitioners strive to develop movement versatility and fluidity, we were frequently ordered to ‘crab walk,’ cartwheel, ‘bear walk’ and a host of other movement techniques that involved getting down and around on the ground.

Head-first, feet-first, sideways, pirouetting, we had to learn to move on all four in the bear walk, practicing by going up and down the length of the academy, across the rough tile floor in a decrepit colonial fort in Salvador. The frequent practice – although still much less than those with Uner Tan – left us with distinctive calluses on our hands; mine spread especially across the pads of each finger and down the metacarpal of the second finger (the middle of the palm). Like those with UTS, we learned to walk with flat hands because, if we tried on fingertips and thumb, our teacher quickly pointed out how it was possible to dislocate the thumb; he sometimes slowly stepped on our hands to flatten them, demonstrating that it was the only stable hand position.

Over time, the practice of bear walking became comfortable. When playing capoeira, trying to avoid being swept to the ground while launching kicks of one’s own, a quadrupedal style of locomotion proves to be useful; switching the conditions of movement can make seemingly odd forms of locomotion efficient. Similarly, when climbing a steep incline, even inexperienced human quadrupeds can find themselves switching to the position

Final thoughts

In fact, when we look at our bodies, we find many structures that are not terribly well adapted to bipedalism. As Wilton Krogman (1952) put it in his article, ‘Scars of Human Evolution’: ‘Our skeleton is such a hodgepodge makeshift that the real wonder resides in the fact that we get along as well as we do.’ 
 We pay a high price for bipedalism: instability, especially on slippery surfaces; increased dangers when we lose some of our sense of balance or leg sensitivity in later life [as I discussed in a much earlier piece on balance problems in older people]; lower back and other spinal problems; varicose veins and circulation issues; nevermind the fragility of a movement system with no backup limbs (unless, like the UTS patients with poliomyelitis, you’re willing to convert to walking on all fours)…

In my previous post on climbing, I pointed out that the idea that bipedalism is ‘obligate,’ absolutely necessary, is belied by people who manage otherwise, whether due to disability or extraordinary ability. Individuals with Uner Tan Syndrome remind us that, however common the ability is, bipedalism is not our only option. The people with ‘facultative quadrupedalism’ — the ones that Prof. Uner Tan kept sending me articles about who don’t seem to have a genetic defect — capoeira practitioners, Johnny Eck, Kurt Fearnley, even Faith and that goat, all demonstrate that other forms of locomotion are possible.

The fact that so many people — virtually every human without congenital leg problems — develops the ability to walk bipedally does not necessarily make it a defining trait of humanity, a condition for inclusion in our species. Clearly, just because someone cannot walk bipedally does not mean that they cease to be human.

Like John Hawks, I don’t think that individuals with Uner Tan Syndrome offer us much, if anything, in the way of insight into human evolution, perhaps because I don’t think quadrupedalism is such an extraordinary trait. Like every other Capoeira Angola practitioner, I’ve done it, a lot. Nor does the fact that the VLDLR gene has been implicated in many of the cases of UTS demonstrate that the gene is crucial to the emergence of bipedalism, it just shows that a messed up VLDLR gene can have some nasty consequences for the cerebellum. Certainly, we can’t long consider the idea that UTS sufferers are examples of ‘reverse evolution’ or evolutionary atavism; it’s unclear that our ancestors ever walked palmigrade on the ground.

Neurological homologies with quadrupedal animals, similarities in the way the nervous system handles bipedal and quadrupedal walking, should not surprise us. We didn’t get a whole new nervous system when our ancestors started getting around on only half their limbs (see Dietz 2002), and gravity and the necessity for rhythmic movement mean that external constraints also provide some stability in structure. Even in neurological ‘normals,’ all you non-quadrupeds out there, Dietz and Michel (2009) found that you use a combination of movements in all four limbs that looks very much like feline quadrupedalism when you have to avoid obstacles.

The individuals with UTS, both the cases with severe genetic anomalies and diverse types of ‘facultative quadrupedalism’ highlighted by Prof. Uner Tan’s dogged curiosity, help us to see one set of unusual variants that the human body and nervous system are capable of becoming. One reason I find human quadrupeds so intriguing is that they remind us how difficult bipedalism is, how much development and de facto training need to go into growing up a nervous system and lower body that can manage such an odd and challenging form of locomotion. Uner Tan’s examples help explain why I’m so interested in athletes: because, at some level, we’re all in training, we just don’t realize it.

Final dancing merengue dog

And if you’re still reading, you can also check out the Amazing Merengue Dog!

Merengue Dog!

Note: Every effort has been made to embed the video clips in the post. Apparently there’s a bug, so I’ve had to settle for links, it seems. Eventually, I’ll get these fixed. Apologies for now.

Additional reading

John Hawks’ early discussion of the Uner Tan Syndrome announcements, especially as they were linked to the BBC TV special on the families: On pathology and evolution, or, the Turkish tetrapods.

Images:

Johnny Eck from the Johnny Eck Museum

Kurt Fearnley photograph from The Age.

References (for both parts 1 & 2):

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Dietz V, & Michel J (2009). Human bipeds use quadrupedal coordination during locomotion. Annals of the New York Academy of Sciences, 1164, 97-103 PMID: 19645886

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Humphrey, Nicholas, Stefan Mundlos, & Seval Türkmen (2008). Genes and quadrupedal locomotion in humans. Proceedings of the National Academy of Science , 105 (21) DOI: 10.1073 pnas.0802839105

Humphrey, N.; Skoyles, J.R. & Keynes, R. (2005). Human hand-walkers: five siblings who never stood up [online]. London: LSE Research Online. Available at: http://eprints.lse.ac.uk/archive/00000463

Hrdlicka, A. 1931. Children who run on all fours, and other animal-like behaviors in the human child. New York: McGraw-Hill.

Krogman, William. 1952. Scars of Human Evolution. Scientific American 185(6): 54-57.

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Tayfun Ozcelik, Nurten Akarsu, Elif Uz, Safak Caglayan, Suleyman Gulsuner, Onur Emre Onat, Meliha Tan, & Uner Tan (2008). Mutations in the very low-density lipoprotein receptor VLDLR cause cerebellar hypoplasia and quadrupedal locomotion in humans. Proceedings of the National Academy of Sciences, 105 (11), 4232-4236 DOI: 10.1073/pnas.0710010105

Ozcelik, Tayfun,, Nurten Akarsu,, Elif Uz,, Safak Caglayan,, Suleyman Gulsuner,, Onur Emre Onat,, Meliha Tan,, & Uner Tan (2008). Reply to Herz et al. and Humphrey et al.: Genetic heterogeneity of cerebellar hypoplasia with quadrupedal locomotion. Proceedings of the National Academy of Sciences, 105 (23) DOI: 10.1073 pnas.0804078105

Stanford CB (2006). Arboreal bipedalism in wild chimpanzees: implications for the evolution of hominid posture and locomotion. American journal of physical anthropology, 129 (2), 225-31 PMID: 16288480

Tan, Meliha, Sibel Karaca, and Uner Tan. (2010). A New Case of Uner Tan Syndrome—with Late Childhood Quadrupedalism. Movement Disorders, 25 (5), 652-653 DOI: 10.1002/mds.22951

Tan, U. (2005). Unertan Syndrome: Quadrupedality, primitive language, and severe mental retardation; a new theory on the evolution of human mind. NeuroQuantology, 4, 250–255. (Abstract and downloadable pdf)

Tan, U. (2006a). A new syndrome with quadrupedal gait, primitive speech, and severe mental retardation as a live model for human evolution. International Journal of Neuroscience, 116, 361–369. (Abstract and downloadable pdf)

Tan, U. (2006b). Evidence for “Unertan Syndrome” and the evolution of the human mind. International Journal of Neuroscience, 116, 763–774. (Abstract and downloadable pdf)

Tan, U. (2006c). Evidence for “Uner Tan Syndrome” as a human model for reverse evolution. International Journal of Neuroscience, 116, 1539–1547. (Abstract and downloadable pdf)

Tan, Uner (2007). A Wrist-Walker Exhibiting No “Uner Tan Sydnrome”: A Theory for Possible Mechanisms of Human Devolution Toward the Atavistic Walking Patterns. International Journal of Neuroscience , 117 (1), 147-156 DOI: 10.1080/00207450600936866

Tan, Uner. 2008. Discovery of Unertan syndrome and reverse evolution: as an “Aha!” experience. NeuroQuantology 6: 80-3. (abstract)

Tan, Uner. 2010. Uner Tan Syndrome: History, Clinical Evaluations, Genetics, and the Dynamics of Human Quadrupedalism. The Open Neurology Journal 4, 78-89. (abstract)

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[Comments on the original post:]

15 Responses to 2 legs good, 4 legs better: Uner Tan Syndrome, part 2

1. Blackbird says:September 5, 2010 at 9:34 pmCool post and I love merengue dog. You don’t mention the fact that most humans go through a cuadrupedal phase when a few months old – granted, even at that stage there is a log of variation and ‘bottom shufflers’ also occur. This developmental ‘crawling’ stage possibly forms a base for all subsequent quadrupedal movement.Rating: 0 (from 0 votes)
   
2. John Wilkins says:September 6, 2010 at 2:15 amExcellent post, but that accent is, so far as I can tell, French-Italian-Boer-Australian-Tongan.Rating: 0 (from 0 votes)
   • gregdowney says:September 6, 2010 at 3:39 amI’m even more polyglot than I thought! Or just a really bad writer of dialogue…Rating: 0 (from 0 votes)
     
3. Billfurnback says:September 6, 2010 at 7:02 amYou Might want to look hereThe interesting thing about these ancestors of australopithecine is they walked on two legs or four as they needed to, and they were palmate walkers when going on four legs.Rating: 0 (from 0 votes)
   
4. Billfurnback says:September 6, 2010 at 7:08 amOh well it would not accept my link to the special issue from 2 October 09. A summery and the reports from the issue is available to non members. It was free last year but now I don’t know.Rating: 0 (from 0 votes)
   
5. hat_eater says:September 6, 2010 at 1:58 pmFascinating. As a side note, the ability to switch to gallop isn’t exclusive to quadrupedal kids, I discovered I could do this when I was about 10 years old.Rating: 0 (from 0 votes)
   
6. Harold says:September 6, 2010 at 3:09 pmInteresting stuff. I recently broke my left leg just above the ankle and it’s amazing how your body will accommodate all the different problems you get from this, like stiff joints, shortened tendons, pain etc.. A big part of my physical therapy at the moment consists of unlearning the wrong method to move you automatically adopt when you favor one leg over the other. As such I agree with your conclusion that UT doesn’t appear to be an evolutionary regression, but is merely an adaptation the body figures out because it is ‘plastic’.I can’t, however, agree with your statement that bipedalism isn’t a defining characteristic of human beings, normally we tend to look at healthy specimens and not pathological ones when determining species.Rating: 0 (from 0 votes)
   
   • gregdowney says:September 6, 2010 at 11:33 pmHarold, I know where you’re coming from on your last point, but I’m a little hesitant to too strongly adhere to the assumption, which you may not be making, that what is ‘pathological’ is easy to identify. Because I’m looking at an evolutionary timeline, by the standards of our species, I suspect that a fairly large proportion of humans alive today would be considered at least mildly ‘pathological’ measured by our species’ potential for mobility. I’m not just thinking about non-Western individuals who might be malnourished or otherwise afflicted, but also of Western individuals with severely limited mobility (again, relative to our ancestors).For example, in areas like climbing or waking without shoes or sprinting or defending oneself, I suspect that, measured against people who haven’t grown up in industrial environments, many Westerners would fall well below any mark of ‘pathological’ in these other settings. Sure, the four families with UTS that were initially reported have severe abnormalities, but I’m coming more from a neurodiversity perspective; don’t deny the condition, but do deny the idea that we can just throw out the variation and see what is truly ‘human,’ based on our own sense of self.If you’re interested, check out the Monkey King post that I linked to at the old site. There, I spend more time on the issue of climbing, modifications to the body, and how patterns of disuse affect us, which I think is especially important considering how important the arboreal-terrestrial transition is thinking about the emergence of modern humans.Rating: 0 (from 0 votes)
     
7. Margaret Wilson says:September 6, 2010 at 3:29 pmWith a background in the psycholinguistics of signed languages, I find the debate over this a little surprising. In the case of signing, it’s uncontroversial that:1) spoken language is a preferred default, but2) when speech is not an option, signing is an obvious alternative that gets “reinvented” over and over; however3) not all deaf people use signing, particularly when they are isolated cases, when there is strong social pressure for them to use oralism, or when they lose their hearing later in life; and finally,4) while proponents of a gestural origin of language find modern signed languages interesting (and probably consider them to be an atavism), no one thinks modern signed languages are proof of the gestural origin theory.This all seems in line with what you are arguing here for quadrupedalism. I’m just surprised that so much arguing is neccessary. Anyway, maybe you’ll find this analogy to signed languages useful in making your case.Rating: 0 (from 0 votes)
   
   • gregdowney says:September 6, 2010 at 11:37 pmHi Margaret — great to see you here!Language is a good case because you’re less likely to get caught up in the argument that what emerges, the adaptation, is somehow an evolutionary ‘reversal.’ However, I would agree with the ‘reversal’ thinking ONLY in that the exaptation of the nervous system probably makes some alternative solutions more likely to emerge than others (that is, some kinds of quadrupedal movement, sign language rather than other signaling system).Actually, it’s a question I’d have for someone more familiar with the signing literature: are there examples of non-signing deaf forms of communication that have arisen in isolate populations? Although pictures or writing might be possible, I’m not even clear what an alternative would look like, and would be interested in thinking about it.Rating: 0 (from 0 votes)
     
8. Uner Tan says:September 10, 2010 at 7:44 am-This is the first and interesting article on the Uner Tan syndrome. However, my recently published review article on the syndrome (see Tan, 2010) seems to be not discussed, e.g., with regard to mutation in VLDLR gene in evolutionary perspective, diagonal-sequence quadrupedal locomotion (QL) with regard to evolution of QL since 400 million years ago, evolution of quadrupedalism and bidepalism, dynamic systems theory with regard to the self-organization process for the emergence of human quadrupedalism like other psychomotor traits…-The theory of human evolution in reverse should be clear if my recent article (Tan, 2010) is carefully read, considering the definition of evolution in reverse (see also the definition in the target article). On the other hand, I am indeed aware of the role of randomness in evolution, considering the dynamic systems theory including the mechanisms of self-organization..-The genetic heterogenetity in UTS is a property shared by many other syndromes (see Tan, 2010, for the minor role of genetics in the emergence of the UTS, as only one element among many others within the system).-On the other hand, the Uner Tan syndrome with the main symptom of the human quadrupedalism, exhibiting “homo quadrupedus”, is not only important for the understanding the ontogeny of bipedal locomotion in human beings, it is also important for the emergence of the “homo erectus” from “homo quadrupedus”…-Below I am presenting some clips from my recently published review article on the Uner Tan syndrome (Tan, 2010), to elucidate some important points:Abstract (p.1):
   
   “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.”Concluding remarks (p. 87):
   
   In this review article the Uner Tan syndrome was analyzed with reference to the main characteristics of the patients with habitual or facultative quadrupedalism and impaired cognition, including intelligence, speech, and conscious experience. Barany’s caloric nystagmus test yielded three different results: normal vestibular system and central or vestibular defect. MRI and PET scans showed a mild gyral simplification in the cerebral cortex, and cerebellar hypoplasia, especially in vermis, except one patient with a seemingly normal brain. It was shown that UTS is heterogeneous regarding the genetics, brain impairment, vestibular defects, and environment, which suggests a multifactorial origin of the syndrome. Uner Tan syndrome was presented as a distinct entity among the well-known non-progressive ataxias, especially DES-H, which is entirely similar to Cayman ataxia. Interestingly, neural patterns for diagonalsequence locomotion of human quadrupeds emerged 400 million years ago as an ancient mode of locomotion, suggesting human quadrupedalism as a deeply conserved adaptive response to impairments in balance. In this context, it was suggested that Uner Tan syndrome may be considered under phylogenetic diseases associated with phylogenetic regression, which, in turn, is closely related to reverse evolution. It was concluded that a dramatic process of adaptive self-organization with rewiring of the nervous system may play a role in the emergence of habitual quadrupedal locomotion during infancy, or even much later in childhood. No previously established neural code, or any other motor program alone may be responsible for the early or late emergence of human quadrupedalism. Considering the dynamic systems theory, the attractor, human quadrupedalism, as an adaptive self-organized motor behavior, may result from the dynamic interaction of many subsystems, such as the spinal central pattern generators, posture, balance, body constraints, muscle strength, extensor and flexor motor systems, perceptual processes, cognition, motivation, genetics and environmental constraints, not depending upon the prior existence of instructions embedded within the central nervous system.Reference
   Tan, U. (2010). Uner Tan syndrome: history, clinical evaluations, genetics, and the dynamics of human quadrupedalism. Open Neurology Journal, 4: 78-89.Rating: 0 (from 0 votes)
   
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11. Mark Riggle says:September 26, 2011 at 6:31 pmComment on the part without explanation:
    “Interestingly enough, the ratio of arm length to leg length was found to be 90% for the quadrupedal man, 83% for the bipedal man with ataxia, and 78% for the quadrupedal woman. Human-like apes have a ratio about 90% or slightly more, Lucy’s ratio was estimated to be 85%, and human have a ratio of around 70%…”
    For the legs to grow long, they need the stress of a bending moment; upright walking will provide that stress. If that stress does not occur, then the legs will be short: as found in children who never walk due to say severe cerebral palsy. So perhaps therefore, the arms in quadruped people may grow longer because of the greater stress on their arms and their legs will be shorter because of less stress.
    The walking stresses also produce the lordosis of the lower spine and hip changes; I would expect those to be different in UTS.
    [I hope somebody still reads this posting]