Evolved developmental homeostasis disturbed in LB1 from Flores, Indonesia, denotes Down syndrome and not diagnostic traits of the invalid species Homo floresiensis

Contributed by Kenneth J. Hsü, May 14, 2014 (sent for review November 21, 2013; reviewed by Alan G. Fix, Robert G. Bednarik, and Judith Hall)
August 4, 2014
111 (33) 11967-11972
Letter
Mandibular evidence supports Homo floresiensis as a distinct species
Michael Carrington Westaway, Arthur C. Durband [...] Mark Collard

Significance

The population that has become known as Homo floresiensis has been described as “the most extreme human ever discovered.” Specimen LB1 from Liang Bua Cave is unusual, but craniofacial and postcranial characteristics originally said to be diagnostic of the new species are not evident in the other more fragmentary skeletons in the sample that resemble other recent small-bodied human populations in the region (including the Andaman Islands, Palau, and Flores itself). Here we demonstrate that the facial asymmetry, small endocranial volume, brachycephaly, disproportionately short femora, flat feet, and numerous other characteristics of LB1 are highly diagnostic of Down syndrome, one of the most commonly occurring developmental disorders in humans and also documented in related hominoids such as chimpanzees and orangutans.

Abstract

Human skeletons from Liang Bua Cave, Flores, Indonesia, are coeval with only Homo sapiens populations worldwide and no other previously known hominins. We report here for the first time to our knowledge the occipitofrontal circumference of specimen LB1. This datum makes it possible to link the 430-mL endocranial volume of LB1 reported by us previously, later confirmed independently by other investigators, not only with other human skeletal samples past and present but also with a large body of clinical data routinely collected on patients with developmental disorders. Our analyses show that the brain size of LB1 is in the range predicted for an individual with Down syndrome (DS) in a normal small-bodied population from the geographic region that includes Flores. Among additional diagnostic signs of DS and other skeletal dysplasiae are abnormally short femora combined with disproportionate flat feet. Liang Bua Cave femora, known only for LB1, match interlimb proportions for DS. Predictions based on corrected LB1 femur lengths show a stature normal for other H. sapiens populations in the region.

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Acknowledgments

We honor the memory of our group’s deceased colleagues, Teuku Jacob and Alan Thorne, whose work was integral to the findings reported here. David Frayer, a surviving member of our original group, merits continuing recognition for being the first to notice LB1 facial asymmetry that led to a cascade of other findings. Amy Seybert elucidated the development and measurement of humeral retroversion and Sarah Tedesco organized extensive background research on carpal bones. Jonathan T. Eckhardt first questioned the probability of finding an uncommon developmental variant in an ancient context, and David A. Eckhardt graciously donated a decade of episodic technical assistance and insight toward resolving this conundrum, as did H. Joseph Sommer. Among other colleagues and friends at Pennsylvania State University, Michael and Jamie Berubé helped provide an uncommon perspective on Down syndrome. Patrick M. Byrne (Overstock.com, CEO) provided financial support at a critical point. The authors accept responsibility for any questions that remain unresolved and encourage other researchers to join us in seeking more open access to the primary specimens that merit further impartial analysis.

Supporting Information

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Supporting Information

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Information & Authors

Information

Published in

Go to Proceedings of the National Academy of Sciences
Proceedings of the National Academy of Sciences
Vol. 111 | No. 33
August 19, 2014
PubMed: 25092311

Classifications

Submission history

Published online: August 4, 2014
Published in issue: August 19, 2014

Keywords

  1. asymmetry
  2. atavism
  3. body mass
  4. body height

Acknowledgments

We honor the memory of our group’s deceased colleagues, Teuku Jacob and Alan Thorne, whose work was integral to the findings reported here. David Frayer, a surviving member of our original group, merits continuing recognition for being the first to notice LB1 facial asymmetry that led to a cascade of other findings. Amy Seybert elucidated the development and measurement of humeral retroversion and Sarah Tedesco organized extensive background research on carpal bones. Jonathan T. Eckhardt first questioned the probability of finding an uncommon developmental variant in an ancient context, and David A. Eckhardt graciously donated a decade of episodic technical assistance and insight toward resolving this conundrum, as did H. Joseph Sommer. Among other colleagues and friends at Pennsylvania State University, Michael and Jamie Berubé helped provide an uncommon perspective on Down syndrome. Patrick M. Byrne (Overstock.com, CEO) provided financial support at a critical point. The authors accept responsibility for any questions that remain unresolved and encourage other researchers to join us in seeking more open access to the primary specimens that merit further impartial analysis.

Authors

Affiliations

Maciej Henneberg
School of Medical Sciences, The University of Adelaide, Adelaide, SA 5005, Australia;
Robert B. Eckhardt1 [email protected]
Laboratory for the Study of Morphology, Mechanics and Molecules, Department of Kinesiology, Pennsylvania State University, University Park, PA 16802; and
Sakdapong Chavanaves
Laboratory for the Study of Morphology, Mechanics and Molecules, Department of Kinesiology, Pennsylvania State University, University Park, PA 16802; and
Kenneth J. Hsü1 [email protected]
Kenneth J. Hsü Center for Integrated Hydrological Circuits Development, National Institutes of Earth Sciences, Beijing 100871, China

Notes

1
To whom correspondence may be addressed. Email: [email protected] or [email protected].
Author contributions: M.H., R.B.E., and K.J.H. designed research; M.H., R.B.E., S.C., and K.J.H. performed research; M.H., R.B.E., and K.J.H. analyzed data; and M.H., R.B.E., and K.J.H. wrote the paper.
Reviewers: A.G.F., University of California, Riverside; R.G.B., International Federation of Rock Art Organisations; and J.H., University of British Columbia.

Competing Interests

The authors declare no conflict of interest.

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    Evolved developmental homeostasis disturbed in LB1 from Flores, Indonesia, denotes Down syndrome and not diagnostic traits of the invalid species Homo floresiensis
    Proceedings of the National Academy of Sciences
    • Vol. 111
    • No. 33
    • pp. 11907-12270

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