In a discovery that could help boost understanding of a rare type of dwarfism, researchers announced today that they have found a genetic culprit for the condition.
But in addition to increasing knowledge of this condition, the researchers' conclusions could also fuel the continuing debate over the origins of a mysterious group of hobbits that walked the earth tens of thousands of years ago.
In the study, released today by the journal Science, an international team of researchers led by Anita Rauch of the Institute of Human Genetics in Erlangen, Germany, examined a number of individuals with a condition known as microcephalic osteodysplastic primordial dwarfism type II — or MOPD II for short.
What they found was that a key mutation in chromosome 21 likely led to the condition — a finding that represents a first-of-its-kind genetic explanation for this type of dwarfism.
"Adults with this rare inherited condition have an average height of 100 centimeters and a brain size comparable to that of a 3-month-old baby, but are of near-normal intelligence," the researchers noted in their article.
Genetic experts not affiliated with the work said the finding offers intriguing hints to the genetic puzzle behind this form of dwarfism.
The study provides scientists a mechanism for the development of this condition, said Anne Bowcock, professor of genetics at the Washington University School of Medicine in St. Louis. "I find it intriguing that alterations in this pathway can result in the characteristics of this disease."
But Bowcock added that it's unlikely that the discovery of this genetic variation will have a practical application in terms of screening and genetic counseling.
"Regarding screening for and detecting genetic abnormalities within this gene in the womb, this is a very rare syndrome, and screening for mutations within this gene in the womb is not practical at this stage," she said.
End of the Hobbit Species?
But as interesting as the findings are to geneticists, the researchers' conclusions at the end of the article could have even bigger implications for the hobbit remains, whose discovery was announced in 2004.
On one side of the debate are those who believe that the diminutive hominids that inhabited Flores Island about 95,000 to 12,000 years ago represented an entirely new species of humans. On the other side are those that contend that a genetic abnormality, perhaps like the one revealed in the new study, is responsible — which would mean that the hobbits would simply be the products of a genetic quirk that affected previously recognized species of humans of the period.
In short, if the hobbits were found to be merely the product of a gene mutation, they would not be accorded the status of a species.
"There is an ongoing debate as to whether the Late Pleistocene hominid fossils from the island of Flores, Indonesia, represent a diminutive, small-brained new species, Homo floresiensis, or pathological modern humans," the researchers wrote, adding that people with MOPD II appear to have several features in common with the hobbits — most notably a height of roughly one meter and certain facial features.
"Given these similarities, it is tempting to hypothesize that the Indonesian diminutive hominids were in fact humans with MOPD II," the researchers noted. "With the identification of the genetic basis of MOPD II, this hypothesis may soon be testable."
But, Charles Hildebolt, a physical anthropologist at Washington University who has worked with Florida State University paleontologist Dean Falk in the study of Homo floresiensis, said that pegging the characteristics of the hobbits to this mutation is an example of a "pathology of the week" in the continuing debate over the origin of the mysterious hominids.
"Chances are, there will be people who jump on the bandwagon with their pathology of the week to explain [the hobbits]," he said. "One just needs to look carefully at the published studies before making wild suggestions.
"I don't think this adds a whole lot to the debate. The claims here do not provide any real data; they just make these suggestions at the end of the paper."
He said that many characteristics of Homo floresiensis identified in other research over the past three years defy the conditions brought about by the gene mutation.
He added that a study led by Falk just last year even compared the brain structure of modern-day dwarfs and normal humans with the likely brain structure of the hobbit. And he says the hobbit brain structure differed from both modern-day examples.
"Obviously the researchers did not read this study."
And Hildebolt added that other characteristics — such as the presence or absence of a chin and prominent brow ridge, or leg length relative to body size — also suggest the hobbits of Flores Island did not owe their appearance and stature to this gene mutation.
He said that with these findings in mind, it would be premature to relegate the existence of Homo floresiensis to a genetic quirk, rather than according them status as a species of their own.
"This pathology has a fun conclusion, but the evidence they provide in support of this conclusion is just not too convincing to me," Hildebolt said.