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A Critical Evaluation of the Down Syndrome Diagnosis for LB1, Type Specimen of Homo floresiensis

Title: A Critical Evaluation of the Down Syndrome Diagnosis for LB1, Type Specimen of Homo floresiensis.
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Name(s): Baab, Karen L., author
Brown, Peter, author
Falk, Dean, author
Richtsmeier, Joan T., author
Hildebolt, Charles F., author
Smith, Kirk, author
Jungers, William, author
Type of Resource: text
Genre: Text
Date Issued: 2016-06-08
Physical Form: computer
online resource
Extent: 1 online resource
Language(s): English
Abstract/Description: The Liang Bua hominins from Flores, Indonesia, have been the subject of intense scrutiny and debate since their initial description and classification in 2004. These remains have been assigned to a new species, Homo floresiensis, with the partial skeleton LB1 as the type specimen. The Liang Bua hominins are notable for their short stature, small endocranial volume, and many features that appear phylogenetically primitive relative to modern humans, despite their late Pleistocene age. Recently, some workers suggested that the remains represent members of a small-bodied island population of modern Austro-Melanesian humans, with LB1 exhibiting clinical signs of Down syndrome. Many classic Down syndrome signs are soft tissue features that could not be assessed in skeletal remains. Moreover, a definitive diagnosis of Down syndrome can only be made by genetic analysis as the phenotypes associated with Down syndrome are variable. Most features that contribute to the Down syndrome phenotype are not restricted to Down syndrome but are seen in other chromosomal disorders and in the general population. Nevertheless, we re-evaluated the presence of those phenotypic features used to support this classification by comparing LB1 to samples of modern humans diagnosed with Down syndrome and euploid modern humans using comparative morphometric analyses. We present new data regarding neurocranial, brain, and symphyseal shape in Down syndrome, additional estimates of stature for LB1, and analyses of inter- and intralimb proportions. The presence of cranial sinuses is addressed using CT images of LB1. We found minimal congruence between the LB1 phenotype and clinical descriptions of Down syndrome. We present important differences between the phenotypes of LB1 and individuals with Down syndrome, and quantitative data that characterize LB1 as an outlier compared with Down syndrome and non-Down syndrome groups. Homo floresiensis remains a phenotypically unique, valid species with its roots in Plio-Pleistocene Homo taxa.
Identifier: FSU_libsubv1_wos_000377561700008 (IID), 10.1371/journal.pone.0155731 (DOI)
Keywords: craniofacial morphology, hominin evolution, human occupation, laron-syndrome, late pleistocene, liang-bua, mental defectives, premature loss, southeast-asia, syndrome phenotypes
Publication Note: The publisher’s version of record is available at http://www.dx.doi.org/10.1371/journal.pone.0155731
Persistent Link to This Record: http://purl.flvc.org/fsu/fd/FSU_libsubv1_wos_000377561700008
Owner Institution: FSU
Is Part Of: Plos One.
1932-6203
Issue: iss. 6, vol. 11

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Baab, K. L., Brown, P., Falk, D., Richtsmeier, J. T., Hildebolt, C. F., Smith, K., & Jungers, W. (2016). A Critical Evaluation of the Down Syndrome Diagnosis for LB1, Type Specimen of Homo floresiensis. Plos One. Retrieved from http://purl.flvc.org/fsu/fd/FSU_libsubv1_wos_000377561700008