August 5, 2014
Scientists Claim Hobbit-Like Remains Belonged To Human With Down Syndrome
redOrbit Staff & Wire Reports - Your Universe Online
Skeletal remains recovered from the Indonesian island of Flores over a decade ago are not a new species of “hobbit” sized human, but an ancient Homo sapien showing signs of abnormal development consistent with Down syndrome, an international team of researchers claim in a new Proceedings of the National Academy of Sciences study.
“The population that has become known as Homo floresiensis has been described as ‘the most extreme human ever discovered,’” the authors wrote in their study. While they said that LB1 was “unusual,” they noted that “craniofacial and postcranial characteristics originally said to be diagnostic of the new species are not evident in the other more fragmentary skeletons in the sample that resemble other recent small-bodied human populations in the region.”
“Here we demonstrate that the facial asymmetry, small endocranial volume, brachycephaly, disproportionately short femora, flat feet, and numerous other characteristics of LB1 are highly diagnostic of Down syndrome, one of the most commonly occurring developmental disorders in humans and also documented in related hominoids such as chimpanzees and orangutans,” they added.
The initial descriptions of Homo floresiensis focused on the unusual anatomical characteristics of LB1, the researchers explained. The creature reportedly had a cranial volume of only 380 milliliters (23.2 cubic inches), indicating that its brain was less than one third the size of an average modern human's, and its short thigh bones suggested that the creature was only 1.06 meters (roughly 3.5 feet) tall.
While some of its traits were characterized as unique and indicative of a new species, others drew comparisons to earlier hominins, including Homo erectus and Australopithecus. After taking a close second look at the evidence, however, the authors discovered the original figure for cranial volume had been underestimated. They reported consistently finding cranial volumes of about 430 milliliters (26.2 cubic inches).
“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,” Robert B. Eckhardt, professor of developmental genetics and evolution at Penn State, said in a statement. Likewise, the original height estimate was based in part on the short thigh bone of the creature, short thigh bones are also common in humans with Down syndrome.
“Unusual does not equal unique. The originally reported traits are not so rare as to have required the invention of a new hominin species,” Eckhardt added. “When we first saw these bones, several of us immediately spotted a developmental disturbance, 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.”
One potential indicator is the fact that the creature has an asymmetrical skull, which Discovery News explained is expected from a person with Down syndrome. In addition, this characteristic is one of many that appear only in the so-called hobbit skeleton, but not in other fossils recovered from the same location, the researchers noted.
“This work 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?” said Eckhardt. “Our reanalysis shows 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.”