Hobbit did not have Down syndrome
An exciting moment took place exactly ten years ago, when a real hobbit called Homo floresiensis was presented to the world. Harsh debates have been continuing since then: who was really found in Liang Bua cave – a unique pigmy representative of our evolutionary line, or a sick human being? Hundreds of articles containing detailed analysis of the hobbit’s skeleton structure were published over time, but apparently, there is something more to say. A recent issue of Proceedings of the National Academy of Sciences had two articles dedicated to the debunking of the Indonesian pigmy story.
These articles are written by people denying the hobbit’s species particulars. Such ideas have a long history, as it has been suggested that a specimen from Liang Bua suffered from Laron Syndrome with a particular mutation of insulin-like growth factor (IGF-1); which had an underdeveloped pituitary gland, microgyria, microcephaly, endemic cretinism, and Majewski osteodysplastic primordial dwarfism type II or some other type of microcephaly. Luckily there are about 200 of them…
The first article is more or less conceptual, focusing on the fact that rare and unique circumstances happen in history. It points out that it is quite possible to find remains of a sick individual at some point of archeological research. However, to declare a new species based on only one specimen with clear evidence of abnormal development is not a good idea.
The second article contains more details. Based on horizontal cranial circumference, the scull’s volume was recalculated. The authors indicate that endocranial volume can be estimated at about 430 ml. The authors emphasize that such a number corresponds with estimates observed among individuals possessing Microcephaly and Down Syndrome at the same time. Such results cannot be presented as random observations. They always derive from accurate calculations. The same microcephaly might also have shortened femur bones and flat feet, as we can also see in the hobbit specimen. Its cranium asymmetry and lack of sphenoid and frontal sinuses are also pointing to the pathological development of this individual. Specificity of its wrist structure is not that unique according to the authors, and in fact is a variation of a norm in modern humans.
As a result, there have never been any hobbits wondering around our planet. Tolkien’s fans can continue using the word “hobbit” in its initial meaning, and the individual from Liang Bua is just another human being who suffered from Down Syndrome.
But, the article is full of inaccuracies which allow further questioning of the authors’ conclusions.
First of all, the authors recalculate endocranial volume from 380 ml to 430 ml and present it almost as a new finding. Foremost, endocranial volume in the original description was measured in cubic cm (although in this specific case it is not that important) and secondly, the application of virtual modeling for this case in 2005 alloweda viewpoint that the hobbit’s brain volume was about 417 cubic cm, and in 2013 it was again recalculated and estimated to 426 cubic cm. Nobody argued with these recalculations! So what is new in this article? Was it the fact that endocranial volume was measured by cranial circumference? It is not clear why the authors wanted to use this measurement when we already have the results of other much more precise methods and estimates?
The authors dedicate a lot of attention to the increased craniofacial asymmetry despite the fact that it was mentioned in virtually every article dedicated to the Indonesian hobbit. It is worth mentioning that a skull was not excavated for over 18,000 years and was reconstructed from multiple pieces, thus it is hard to expect it to be completely symmetric. Besides, any skull has a certain degree of asymmetry which sometimes could be quite noticeable, even if a person does not suffer from any kind of pathology. We should also take into account that this individual lost a second right lower premolar tooth, suffered from a broken right zygomatic arch, and had at least three traumas of a cranial vault bone during his lifetime. It is possible that craniofacial asymmetry had resulted from given traumas and the fact that the individual had to chew predominantly by the left mandible.
It is sad to acknowledge that the authors again use the hobbit’s brachycrania as the main supporting argument for their theory. Moreover, they refer to it as “brachycephaly” in the article, and in the “Supporting Information” section of the article this parameter’ is called “cephalic,” when in reality, we are dealing with brachycrania and cranial parameter, as “-crania” and “-cephalic” are in fact two quite distinct parameters. The first one is determined by the cranium remains, while the second derive from head measurements of an alive human being. Because of temporal muscles, the head width in relation to a cranium in a living human increases more than its length.
Apparently, the authors did not take a course in cranial development (as a part of anthropometry), or if they did, they probably have skipped a lot of lectures.
In reality, the hobbit’s brachycrania does not prove anything. Foremost, this characteristic is not that reliable, which was certainly proven during the XIX century (especially when dealing with a single specimen) and secondly, individuals with a low height tend to have brachicrania, no matter their origin or absence/presence of pathology.
It is worth questioning why do the authors ignore other findings from Liang Bua? New articles state that Homo floresiensis was described as a single specimen. The LB6/1 mandible has exactly the same characteristics (e.g. absence of an external bony chin, small size, and very low and relatively wide mandible ramus) and is remarkably different from a “standard” human mandible. Should we then assume that there were two individuals with Down syndrome living in a cave? We see mentioning of these and other findings in the article, but they are declared being “normal”, not having asymmetry or any other evidence of pathological development.
Finally, the authors’ argumentation in general seems to be a bit weird: “we found that brain size is consistent with that of a person suffering Down syndrome, plus we can take into account the shortened femur and flat foot. But, if we recalculate the femur in analogy to a femur of a healthy human, it will fall within parameters of a normal human!” Such reasoning looks more like an attempt to stretch the evidence in favor of a given hypothesis.
In conclusion, if the authors are right and there were not any hobbits in Flores, the given arguments do not seem convincing and they leave much space for improvement. Especially if we take into account the fact that most “evidence” discussed by the authors’ were previously mentioned and discussed multiple times by many specialists from both – “endemic species” and “pathological development” camps.
It looks like we are waiting for a published response from the other group of researchers, who described the hobbit as a unique species.
Translated by Olga Vasileva
Special thank you for final editing to Ella Jones.
- Eckhardt R.B., Henneberg M., Weller A.S. et Hsü K.J. Rare events in earth history include the LB1 human skeleton from Flores, Indonesia, as a developmental singularity, not a unique taxon // PNAS, 2014.
- Henneberg M., Eckhardt R.B., Chavanaves S. et Hsü K.J. Evolved developmental homeostasis disturbed in LB1 from Flores, Indonesia, denotes Down syndrome and not diagnostic traits of the invalid species Homo floresiensis // PNAS, 2014.