Did the Hobbit have Down syndrome?

What is the hobbit? No, not Tolkien’s Hobbits, the hobbit, the bones of the singular little 17,000 year-old person unearthed on the Indonesian island of Flores a decade ago.

The discovery team declared it a new human species and called it Homo floresiensis. From the beginning, though, some paleoanthropologists professed to be baffled by the find. Others were certain it was not a new human species at all. Instead, they saw a member of our own species, Homo sapiens, with some sort of developmental disorder that would explain its oddest features (like the asymmetry of its face) and its very small brain (about a third the size of ours, smaller than some chimpanzees.)

As you may have heard, there is no more combative scientific field than paleoanthropology, the study of Homo sap‘s origins and predecessors. The latest volley in this particular battle was fired last week, in two papers published in the Proceedings of the National Academy of Sciences.

They concluded, based on studies of hobbit bones, that the originally reported measurements were erroneous. According to the new studies, the hobbit’s height was at the low end of normal for the region, where people are naturally short. Its brain, the researchers said, was a little bigger than originally reported (although still much smaller than normal).

They surmise that the hobbit, officially designated LB1, was a member of our own species with Down syndrome. Down syndrome is a genetic disorder, occurring when a person possesses an extra copy, or partial copy, of chromosome 21.

Down syndrome is one of the most common developmental abnormalities (occurring in something like 1 in 700 births.) It happens in other primate species besides humans; chimpanzees, for instance. About 6000 Down syndrome babies are born each year in the US. The incidence has been declining because a noninvasive test for Down syndrome is now routine in pregnancy. A confirmed diagnosis of Down syndrome in the fetus often leads prospective parents to terminate the pregnancy.

Hobbit abnormalities

From the beginning some researchers believed that the hobbit looked so odd because it was abnormal in some way. Ralph Holloway, of Columbia University, who has studied an endocast, a cast of the inside of its skull, has said the brain’s small size and some other features hint at pathology.

Like several other researchers, Holloway has tried (and failed) to find direct correspondences between the hobbit’s cranium and those of people known to have microcephaly. Microcephaly, meaning simply small head, is an umbrella term for a miscellany of conditions with scores of different genetic and environmental causes and myriad manifestations.

It has not been possible, though, to match any of the known syndromes involving microcephaly with the hobbit, although some microcephalic syndromes share some features with it, including stature, head size, and anomalies of jaw and teeth. In a 2013 paper comparing the hobbit with normal and microcephalic humans, Holloway and his colleagues concluded that an endocast of its skull was more similar to microcephalic skulls than to normal ones.

Still, nothing so far unearthed in the clinical literature or the fossil record matches the hobbit’s peculiar head. The discoverers have argued that the head deformities are the result of being buried under several meters of sediments for several thousand years, which could certainly be true. Still, deformity of some kind cannot be ruled out, including a cranial shape unique to hobbits. Isolated populations routinely develop distinctive features.

Who are the hobbit’s ancestors?

The discovery team suggested originally that LB1 might have been descended from Homo erectus, a prodigiously traveled early human who got from the human birthplace in Africa as far as Indonesia by nearly 2 million years ago. Researchers later described anatomical similarities–with the hobbit pelvis, for example–to Australopithecus, an even earlier forebear whose most famous example is the African fossil Lucy, dated at more than 3 million years ago.

At least a genetic link to H. erectus is not outrageous geographically, since H. erectus had been in the region for so long. In fact, the type specimen of H. erectus was found more than a century ago on the Indonesian island of Java.

But, unlike big-brained erectus, whose brain was 75% of the size of ours, there is no evidence whatever that small-brained Australopiths (35% the size of ours) ever ventured out of Africa—let alone invented boats and sailed off to Indonesia more than 3 million years ago. Yet something like this astounding seagoing scenario—a really, really ancient mariner—seems to be required if H. floresiensis had Australopith ancestry.

What about hobbit DNA?

What would settle this argument in a moment–indeed, maybe the only thing that will settle it–is DNA. Did the hobbit possess an additional 21st chromosome or part of one? If yes, Down syndrome. Is the hobbit’s DNA like ours? If yes, H. sapiens. If no, then maybe another human relative? Related to us as Neandertals are, or the mysterious Denisovans, and presumably entitled to be known as H. floresiensis?

You are saying to yourself, why don’t these folks go after the hobbit’s DNA? Well, they have done. Several times. In 2006, two teams tried–and failed–to get DNA from one of the hobbit teeth. At least one other attempt was made in 2011, this one on a tooth said to have been excavated from the site in 2009. This effort was announced in a 2011 Nature news article. No paper has appeared, which leads me to infer that it was probably unsuccessful too.

Techniques for recovering and analyzing ancient DNA are improving all the time, so never say never. But the prospects for recovering hobbit DNA are gloomy at a minimum. Conditions at the Flores excavation site are hot and wet, the worst possible for preserving DNA.

The hobbit is repeatedly referred to as a fossil, but in fact it was never fossilized, a process where minerals in groundwater enter buried bones and, under pressure and over time, turn them stone-like. When hobbit bones were recovered, they were described as being like wet blotting paper. Doesn’t sound hopeful, does it?

In the 1950s, the great Louis Leakey and his colleagues found fossils of a human-like toolmaker who lived in the Rift Valley in Tanzania more than 2 million years ago. Eventually the toolmaker was named Homo habilis, handy man. Today, more than 50 years later, paleoanthropologists are still arguing over whether handy man truly belongs to Homo at all, or should be assigned to some other genus.

That sort of disputatious history is typical in the study of human evolution. In the case of the hobbit, the combatants have staked out their positions, each side sure that it’s correct. The rest of us may never know for certain whether the hobbit is a new human species or just one of us with a developmental disorder–unless the ancient DNA folks can work some of their technical magic and tell us more.

Tabitha M. Powledge is a long-time science journalist and a contributing columnist for the Genetic Literacy Project. She also writes On Science Blogs for the PLOS Blogs Network. Follow her @tamfecit.

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