A new study has found that the diminutive human species whose fossilised remains had been discovered on the Indonesian island of Flores in 2003 did not suffer from Down syndrome — contradicting an earlier claim by researchers who diagnosed Homo floresiensis with the genetic disorder.
An international team of researchers, led by Karen Baab of Midwestern University in the US, analysed features from across the skeleton to convincingly demonstrate that LB1 — the most complete individual recovered and nicknamed the “Hobbit” — did not have Down syndrome.
The team compared physical traits preserved in the skeleton of LB1 to those found in Down syndrome.
In addition to measuring individual bones, the scientists used CT scanning to reconstruct the brain and view internal structures of the skull, as well as assessing the 3-dimensional (3D) shape of the skull.
While people with Down syndrome are not identical to one another, it was nevertheless clear that LB1 was very distinct from all humans, including those with Down syndrome.
The study, published recently in the journal PLOS ONE, found that LB1’s brain was much smaller than that seen in Down syndrome individuals. Likewise, the shape of the skull vault, which surrounds the brain, and chin anatomy were both outside the range seen in humans, with or without Down syndrome.
The diminutive LB1 individual, estimated to be just over a metre (1.09 m) in height, was well below the height range of comparable individuals with Down syndrome.
In fact, females with Down syndrome from Turkey reach a comparable height as the adult LB1 by 6.5 years of age and are considerably taller as adults (1.45 metre on average).
Moreover, the femur is disproportionately short in LB1 relative to the feet and arms compared to all humans, regardless of whether they have Down syndrome.
“The skeletal evidence overwhelmingly contradicts a diagnosis of Down syndrome. Rather, our study is yet further evidence that Homo floresiensis was a distinct species with a fascinating, if somewhat nebulous, evolutionary history,” the researchers said.