Human quadrupeds, primate quadrupedalism, and Uner Tan Syndrome.

Whitney G Cole,Yuri P Ivanenko,Liza J Shapiro,Karen E Adolph,Jesse W Young,David A Raichlen,Scott R Robinson

doi:10.1371/journal.pone.0101758

Whitney G Cole, Yuri P Ivanenko + Show 5 more

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https://doi.org/10.1371/journal.pone.0101758

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Abstract

Since 2005, an extensive literature documents individuals from several families afflicted with “Uner Tan Syndrome (UTS),” a condition that in its most extreme form is characterized by cerebellar hypoplasia, loss of balance and coordination, impaired cognitive abilities, and habitual quadrupedal gait on hands and feet. Some researchers have interpreted habitual use of quadrupedalism by these individuals from an evolutionary perspective, suggesting that it represents an atavistic expression of our quadrupedal primate ancestry or “devolution.” In support of this idea, individuals with “UTS” are said to use diagonal sequence quadrupedalism, a type of quadrupedal gait that distinguishes primates from most other mammals. Although the use of primate-like quadrupedal gait in humans would not be sufficient to support the conclusion of evolutionary “reversal,” no quantitative gait analyses were presented to support this claim. Using standard gait analysis of 518 quadrupedal strides from video sequences of individuals with “UTS”, we found that these humans almost exclusively used lateral sequence–not diagonal sequence–quadrupedal gaits. The quadrupedal gait of these individuals has therefore been erroneously described as primate-like, further weakening the “devolution” hypothesis. In fact, the quadrupedalism exhibited by individuals with UTS resembles that of healthy adult humans asked to walk quadrupedally in an experimental setting. We conclude that quadrupedalism in healthy adults or those with a physical disability can be explained using biomechanical principles rather than evolutionary assumptions.

Highlights

In 2005, Uner Tan described a Turkish family with 19 siblings, five of whom exhibited ‘‘Uner Tan Syndrome’’ or ‘‘UTS’’, characterized by impaired cognitive abilities, dysarthric speech, cerebellar hypoplasia, and habitual quadrupedal gait on hands and feet
Among the lateral sequence strides, 85% were in diagonal couplets (LSDC), 3.5% were in singlefoot (LSSF), and 12% were in lateral couplets (LSLC) (Table 2; Figs. 2, 3)
We have shown that the quadrupedalism used by individuals with UTS resembles that of healthy human adults asked to walk quadrupedally in an experimental setting, and neither group prefers the diagonal sequence/diagonal couplets gait characteristic of nonhuman primates

Summary

Introduction

In 2005, Uner Tan described a Turkish family with 19 siblings, five of whom (ages 14–32 years) exhibited ‘‘Uner Tan Syndrome’’ or ‘‘UTS’’, characterized by impaired cognitive abilities, dysarthric speech, cerebellar hypoplasia, and habitual quadrupedal gait on hands and feet. A key claim used in support of the ‘‘devolution’’ hypothesis is that the form of quadrupedalism used by individuals with UTS resembles that of nonhuman primates (hereafter referred to as ‘primates’), representing a reversal to a ‘‘primitive’’ state. A recent paper acknowledged that ‘‘the genetic associations hitherto reported for the UTS seem to have no or only minor explanatory power, if any, for the origins of human quadrupedalism’’(page 89 [32]), and acknowledged the role of other factors such as socioeconomic status, researchers continue to make persistent (but unsupported) claims regarding the ‘‘primitive’’ and ‘‘primate-like’’ nature of the quadrupedalism [1,9,11,13,14,17,18,19,20,31]. We show that the quadrupedal kinematics exhibited by humans with UTS has been erroneously described as primate-like by the authors, further weakening the ‘‘devolution’’ hypothesis put forth in this series of papers

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