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Did the 'hobbit' human have Down syndrome?

Posted by Hayley Dunning on Aug 7, 2014 1:11:02 PM

A group of bones discovered ten years ago in Indonesia were determined to be a new human species that lived about 17,000 years ago. The only skull, with very small proportions, earned the species the ‘hobbit’ nickname.


Now, a new paper suggests that the hobbit is just an individual with Down syndrome, but Museum human origins expert Prof Chris Stringer doubts the conclusions.


The find, on the island of Flores, included bones from several individuals, but only one had a complete skull and leg bones, from which the original calculations of height and brain capacity were made.


Standing at approximately 1.06m (3.5ft) tall and with a brain only a third of the size of modern humans, the bones seemed to belong to a new species, which was named Homo floresiensis.



A copy of the Homo floresiensis skull.
Credit: Ghedoghedo, Wikimedia Creative Commons.


A new analysis of the skull and thigh bones, published this week in a paper in the journal Proceedings of the National Academy of Sciences USA (PNAS), suggests that these estimates are too low, and a slightly bigger individual actually lies within the range of modern humans with Down syndrome.


The authors support their claims with other evidence, including the asymmetry of the skull, a condition common in modern individuals with Down syndrome. They conclude this one individual had a developmental disorder, and all the remains were in fact modern humans.


Still a new species?


However, Prof Stringer is sceptical of the conclusions. Although there are no other complete skulls, there is another jaw that has similar proportions and characteristics.


Both appear to have no chin, instead showing internal bony reinforcements similar to those found in prehuman fossils from at least two million years ago. This feature is not found in Down syndrome. The wrist bones of two individuals also show features previously unknown in humans from the last one million years, further indicating a unique species.


Weight of evidence


New human species are often difficult for the scientific community to accept, especially from so few bones. Prof Stringer, however, sees parallels between the stories of H. floresiensis and the Neanderthals, originally described from a single site:

A number of pathological conditions were advanced to explain away the distinctive morphology of the Neander Valley skeleton, but other finds gradually forced the acceptance of the Neanderthals as a distinct and extinct human group.

Prof Stringer acknowledges that more H. floresiensis individuals are needed to establish the range of sizes and shapes there may have been, but he thinks this new analysis does not shake the foundations of the species:

In my view this paper does not provide a sound basis to challenge the basic conclusion that a primitive human-like species persisted on the island of Flores within the last 100,000 years.


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