Quadrupedal People Do Not Walk Like Chimpanzees

News to Know

by Dr. Elizabeth Mitchell on August 14, 2014
Featured in Answers in Depth


Uner Tan syndrome does not harbor the evolutionary “how” of human bipedality.

Can people that must walk on all fours tell us about our supposed evolutionary past? Believe it or not, this has been—and still is—a topic of ongoing controversy among evolutionists since Uner Tan syndrome was discovered in a remote corner of Turkey in 2005.

New research reveals that contrary to Dr. Uner Tan’s claims, victims of this disorder do not walk like chimpanzees. This discovery dismantles the primary piece of “evidence” evolutionists have used to support their de-humanizing description of this disorder.

Reverse Evolution?

In 2005 Dr. Uner Tan discovered five mentally retarded siblings in Turkey with a mysterious disease compelling them to bear-walk on all fours. He asserted their walk was “devolution”—that it recapitulates the walk of ancestral primates, that it is “an atavistic expression of our quadrupedal primate ancestry.”1 He and other evolutionists have also asserted that the association of this quadrupedal disorder with mental retardation demonstrates a connection between the evolution of bipedality and higher brain functions. The key piece of evidence offered in support of this claim has been that people with Uner Tan syndrome walk with the same distinctive pattern seen in non-human primates, such as chimpanzees.

BBC image

These people are among the first to be discovered with Uner Tan syndrome, a rare condition that results in human quadrupedalism. Some claim their disability will reveal how humans evolved bipedalism. Photo from BBC.

Many evolutionists have since pointed out that “reverse evolution” does not happen. They nevertheless cling to the idea that if the autosomal recessive mutation associated with Uner Tan syndrome can be precisely characterized, the evolutionary basis for human bipedality will be established. Some evolutionists believe this disability holds clues to how humans evolved from knuckle-walking quadrupedal ape-like ancestors to walk upright.

Quadrupedal Constellation

At its most extreme, Uner Tan syndrome is associated with cerebellar hypoplasia with loss of balance and coordination, mental retardation, and a habitual hand-and-foot quadrupedal gait.2 Even the discovery that the genetic abnormality is not invariably associated with quadrupedalism fueled the controversy, as some evolutionists took that as an indication that both genetic deficiency and environmental factors were involved in the evolution of human bipedalism and brain power.

Neither “forward,” upward human evolution from ape-like ancestors nor devolution has ever happened. And even if victims of this rare disorder really did walk like animals, that would not demonstrate anything about human evolution. Nevertheless, it is heartening to see that a scientist has for the first time actually made quantitative observations to test Uner Tan’s claims and found them wanting.

Primate Gait?

Despite Uner Tan’s claim that people with Uner Tan syndrome walk like non-human primates, a claim perpetuated by a BBC production The Family That Walks on All Fours: Human Quadrupeds that aired on NOVA in 2006, people with Uner Tan do not walk like apes. They walk the same way healthy adult humans typically walk when asked to “bear walk” on their palms and feet. Despite the importance accorded to this bit of “evidence” by evolutionists, until recently no one had ever actually used observational science to establish the truth of this convenient evolutionary claim.

Fossils cannot walk bipedally or any other way, and interpretations of anatomical clues about how extinct animals or people walked are often heavily influenced by evolutionary biases.

To discover how people with Uner Tan walk, University of Texas anthropologist Liza Shapiro and colleagues studied video footage3 of the original Turkish family’s five adult victims as well as two other people with the disorder. They analyzed 513 strides and found that despite all the hype 99% of Uner Tan strides were laterally sequenced steps, which is the pattern used by healthy humans most of the time when on all fours.

The researchers concluded that the locomotion patterns of the Turkish subjects did not match diagonal sequences of non-human primates. Apparently, Uner Tan used still images, leading him to believe it was a diagonal sequence gait, when it was in reality a lateral sequence gait with diagonal couplets.

Gait Sequences and Couplets

Dr. Shapiro may have determined how Uner Tan erred in his description. If a hand and foot land at the same time, that is called a couplet. Dr. Shapiro believes Uner Tan erred in his original, non-quantified, general assessment of the Uner Tan gait because he confused instances of diagonal coupling with diagonal sequence. Some evolutionists confusing gait couplets and gait sequence have even tried to claim a connection to the neural circuitry in ancestral tetrapodal fish!1 (Read more about the complete disconnect of such fishy evolutionary claims from reality in “Did Tiktaalik’s Pelvis Prepare Fish to Walk on Land?”)

Lateral and diagonal couplets are very variable and not at all diagnostic of human-like or animal-like gait. Each form of couplet offers a functional advantage in certain circumstances. Diagonal couplets with lateral sequence—allowing the opposite hand and foot to land at the same time even though the sequence of steps is still lateral—actually aids balance. Dr. Shapiro writes, “The use of diagonal couplets in adult humans walking quadrupedally can thus be explained on the basis of biomechanical considerations, without the need to invoke evolutionary ‘atavism.’”1

In any case, Dr. Shapiro and colleagues conclude that the walk of people with Uner Tan has nothing to do with evolution but is merely an adaptation to their deficiencies that is anatomically and biomechanically functional. They write, “Thus, as with nonhuman mammals, quadrupedal gait preferences in humans are best understood as a function of biomechanical constraints, rather than genetic mutations. We agree with researchers who have pointed out that the use of habitual quadrupedalism in individuals with UTS is an adaptation to instability of the trunk caused by cerebellar dysfunction, combined with environmental conditions such as insufficient medical care.”

Dr. Shapiro has now effectively disproved the evolutionary claim that people with Uner Tan syndrome walk like animals—our supposed ape-cousins. Actually, another distinction should have already been obvious—apes walk on their knuckles, not their palms—but those wishing to maintain the evolutionary connection likened the Uner Tan walk to the way chimps move through trees where they must use the palm side of their hands.

Fossils cannot walk bipedally or any other way, and interpretations of anatomical clues about how extinct animals or people walked are often heavily influenced by evolutionary biases. Therefore, since Uner Tan syndrome was discovered, evolutionists have maintained that Uner Tan would go farther than fossils4 at demonstrating how humans learned to walk upright and even how to think on their feet enough to become human. Unfortunately, some will likely still look to people with Uner Tan for proof of how humans supposedly evolved bipedality.

Brain and Bipedality

Likewise into the trash heap of evolutionary absurdities should go the notion that acquisition of higher brain function in humans was linked to becoming bipedal. Some evolutionists see in Uner Tan syndrome an answer to the evolutionary conundrum of what triggered ape-like ancestors to rise, take up their tools, and walk, claiming that ape-like ancestors learned to walk upright in order to have their hands free for other pursuits. Dr. Uner Tan has expressed this notion, stating that this family—wherein mental deficiencies are combined with quadrupedalism— “may provide us with some important clues about the transition from quadrupedality to bipedality, along with the evolution of the human mind.”5 The link between mental deficiency and quadrupedal walking is just too enticing for evolutionary thinkers who already believe that bipedality and the evolutionary acquisition of higher intellectual powers must have been historically linked millions of years ago.

Yet biologically there is no mechanism by which an animal can acquire the genetic information or the intellectual toolkit to become human just by figuring out how to free its hands and walk on two legs. Furthermore, people with Uner Tan syndrome are fully human whether they suffer mental retardation or not. In the originally publicized account of the first family discovered to have the disorder, one of the young women expressed her wishes and dreams. Animals do not talk about their hopes for the future. To compare these people with animals is cruel and counterproductive.

Problems with Evolutionary Assumptions

The story of Uner Tan syndrome is a graphic illustration of the problem with evolutionary assumptions. The question is not—and never should have been—whether these people were examples of backwards human evolution or case studies that could prove how humans came to walk on two legs in the first place. The link between mental deficiency and quadrupedal walking was just too enticing for evolutionary thinkers who believe that bipedality and the evolutionary acquisition of higher intellectual powers were historically linked millions of years ago.

We can at least be thankful that a more thoughtful and thorough anthropologist has now broken the “ancestral animal” assertion with firm observational evidence. But nothing about Uner Tan syndrome—whether the people walk like primate animals or not—should have ever made scientists look for evolutionary answers or evolutionary evidence in the genes, behavioral backgrounds, or social structure surrounding these people. Their affliction will not offer evolutionary answers and neither will their affliction benefit from evolutionary assumptions.

People with Uner Tan Syndrome are more human victims of the suffering that affects every single one of us and has since the sin of Adam, from whom both they and we all are descended. Perhaps the funding and effort that has been invested by those seeking evolutionary answers in this syndrome would have been better spent in identifying the underlying causes and natural history of the disorder and in seeking ways to help them and future victims function better and maximize their potential for a full rich life.

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  1. L. Shapiro et al., “Human Quadrupeds, Primate Quadrupedalism, and Uner Tan Syndrome,” PLoS ONE 9, no. 7:e101758, doi:10.1371/journal.pone.0101758.
  2. Not all “hand-walkers” are equally affected. The cognitive deficits are not universal, and some patients are able to walk upright at times. At least one other unrelated family in Turkey has been diagnosed by Dr. Uner Tan, and several unrelated cases of varying severity have been discovered elsewhere. For the purposes of the study, Dr. Shapiro limited the observations to patients with irrefutable cases of Uner Tan syndrome and confined the statistical analysis to the original five patients to ensure results were not biased by inclusion of small numbers of patients with varying degrees of severity.
  3. Access to original video and new footage: http://www.utexas.edu/news/tag/uner-tan/feed.
  4. In the documentary aired on NOVA, scientists from the American Museum of Natural History expressed this sentiment.
  5. Quoted from page 251 of Uner Tan, “Unertan Syndrome quadrupedality, primitive language, and severe mental retardation: A new theory on the evolution of human mind,” NeuroQuantology 4 (2005): 250–255 in L. Shapiro et al., “Human Quadrupeds, Primate Quadrupedalism, and Uner Tan Syndrome,” PLoS ONE 9, no. 7:e101758, doi:10.1371/journal.pone.0101758.


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