Another Hobbit paper argues against Down Syndrome theory

No Comments

While the excitement was brewing over the discovery of 700,000-year-old hobbit bones in Flores, another paper published at the same time evaluates the theory that H. floresiensis presented with signs of Down Syndrome. The paper noted significant differences between the hominid bones and those with Down Sydrome and concluded that the bones were unique.

A Critical Evaluation of the Down Syndrome Diagnosis for LB1, Type Specimen of Homo floresiensis
PLoS One, 08 June 2016, doi:10.1371/journal.pone.0155731

Homo floresiensis Remains Unique, Valid Species
Sci-News, 13 June 2016

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.

Full story here.

New paper argues against claims of Hobbit Down Syndrome theory

No Comments
Skull of LB1. Source: The Conversation 20150210

A new paper in PNAS tears down the arguments made last year in the same journal about the Hobbit being a human with Down Syndrome. The arguments centre around the attributes of LB1 and LB6’s chins. The Conversation piece by the same authors breaks it down nicely.

Skull of LB1. Source: The Conversation 20150210

Skull of LB1. Source: The Conversation 20150210

Down syndrome theory on Hobbit species doesn’t hold to scrutiny
The Conversation, 10 February 2015

Mandibular evidence supports Homo floresiensis as a distinct species
Proceedings of the National Academy of Science, doi: 10.1073/pnas.1418997112

Henneberg et al. (1) and Eckhardt et al. (2) present another pathology-based alternative to the hypothesis that the “hobbit” fossils from Liang Bua, Indonesia, represent a distinct hominin species, Homo floresiensis. They contend that the Liang Bua specimens are the remains of small-bodied humans and that the noteworthy features of the most complete specimen, LB1, are a consequence of Down syndrome (DS). Here, we show that the available mandibular evidence does not support these claims.

Absence of chins in the two mandibles recovered at Liang Bua, LB1 and LB6, is a key issue (1, 3). That these specimens lack chins has been argued to preclude their attribution to Homo sapiens, because a chin is widely accepted to be a defining characteristic of our species (3). Henneberg et al. reject this argument on the grounds that a chin is often absent in living Australo-Melanesians. However, the evidence they present does not support their assertion regarding Australo-Melanesian mandibular morphology. One of two studies they cite has not been peer reviewed (the publication is just a conference abstract), whereas the other one has been severely criticized (4). Henneberg et al. also imply that a mandible from Roonka, Australia, supports their claim, but a CT scan of this specimen shows that it has a positive chin (Fig. 1). Thus, there is no reason to believe that living Australo-Melanesians often lack chins and therefore no reason to overturn Brown and Tomoko’s (3) assessment that the absence of chins in LB1 and LB6 precludes their attribution to H. sapiens.

The link to the paper here.

Criticisms over the hobbit-Down Syndrome paper

No Comments

There seems to be more than meets the eye with the latest paper in PNAS on the ‘hobbit’ as a person with Down syndrome. The Guardian has a story on the criticism and reactions to this paper.

Homo floresiensis

Homo floresiensis: scientists clash over claims ‘hobbit man’ was modern human with Down’s syndrome
The Guardian, 17 August 2014
Read More

More Hobbit stories

No Comments

Two articles on the New York Times and the Daily Mail about the recent papers in PNAS suggesting that the ‘Hobbit’ is person with Down syndrome and not a new species.

LB1 skull

A New Explanation for ‘New’ Man
New York Times, 04 August 2014

The oldest case of Down’s syndrome? 15,000-year-old ‘Flores man’ bones are not evidence of a new human species, study reveals
Daily Mail, 05 August 2014
Read More

New study suggests Hobbit was a person with Down syndrome

No Comments

A new study in PNAS suggests that Homo floresiensis may not be a new species, but the skeletal features resemble a normal human with Down syndrome. This one is bound to be controversial for sure!

Flores

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, 04 August 2014
doi: 10.1073/pnas.1407382111

The “hobbit” human not a separate species, say scientists
Popular Archaeology, 04 August 2014

Flores bones show features of Down syndrome, not a new ‘Hobbit’ human
Science Daily, 04 August 2014

‘Hobbit’ had Down syndrome
The Australian, 05 August 2014

Did the ‘Hobbit’ have Down syndrome?
ABC Science, 05 August 2014
Read More