The so-called "Hobbit" human skeleton found in 2004 and heralded as a previously unknown human species was actually that of a normal human with Down syndrome, says a report out this week by an international team of scientists.
According to a statement from Penn State University, the team of researchers performed a rigorous and detailed analysis of the bones and the claims associated with them and determined that what scientists had hailed as Homo floresiensis, a previously unknown species of human, doesn't represent a new species after all, but is actually the skeleton of a "developmentally abnormal" child.
Robert B. Eckhardt, professor of developmental genetics and evolution at Penn State, Maciej Henneberg, professor of anatomy and pathology at the University of Adelaide, and Kenneth Hsü, a Chinese geologist and paleoclimatologist, led the inquiry into the claims regarding Homo florensiensis. The skeletal specimen -- known as LB1 -- was found in Liang Bua cave on the Indonesian island of Flores.
"The skeletal sample from Liang Bua cave contains fragmentary remains of several individuals," said Eckhardt. "LB1 has the only skull and thigh bones in the entire sample."
In 2013, a group of scientists excitedly declared that LB1 heralded the discovery of "tiny people from Flores" who were not "diseased modern humans."
“The new species of human stood approximately 3′ 6″ tall, giving it its nickname ‘The Hobbit,’” wrote researcher Caley Orr in a paper for the Journal of Human Evolution.
In two papers for the Proceedings of the National Academy of Sciences (PNAS), Eckhardt's team attempted to debunk the idea that a separate species of human evolved on the Island of Flores.
The pro-Homo florensiensis contingent said that the dwarf species had "a cranial volume reported as only 380 milliliters (23.2 cubic inches), suggesting a brain less than one third the size of an average modern human's and short thigh bones, which were used to reconstruct a creature standing 1.06 meters (about 3.5 feet tall)."
Eckhardt's team said that that initial estimates of cranial volume and physical stature were "markedly lower than any later attempts to confirm them."
"The difference is significant, and the revised figure falls in the range predicted for a modern human with Down syndrome from the same geographic region," said Eckhardt.
The traits found in the LB1 skeleton, he said, are unusual, yes, but "unusual does not equal unique. The originally reported traits are not so rare as to have required the invention of a new hominin species."
"When we first saw these bones, several of us immediately spotted a developmental disturbance," Eckhardt explained, "but we did not assign a specific diagnosis because the bones were so fragmentary. Over the years, several lines of evidence have converged on Down syndrome."
His team's work, Eckhardt said, "is not presented in the form of a fanciful story, but to test a hypothesis: Are the skeletons from Liang Bua cave sufficiently unusual to require invention of a new human species?"
The team concluded that "they are not. The less strained explanation is a developmental disorder. Here the signs point rather clearly to Down syndrome, which occurs in more than one per thousand human births around the world."