Island of the Tiny People

In 2003, the field of human evolution was rocked by the discovery of “hobbits,” an ancient species of human relatives who stood barely more than a meter tall. Named Homo floresiensis, they lived on the Indonesian island of Flores, and for years researchers argued over whether they represented the first-known human case of “island dwarfism” or if these ancient individuals had some sort of disease causing their short stature. If they were diseased, what disease did they have? If they were a legitimate species, where did they come from?

The disease hypothesis has mostly fallen out of favor. Numerous studies have countered suggestions that H. floresiensis had microcephaly or hypothyroidism or other proposed conditions. On Wednesday, a new study provided evidence against Down Syndrome being responsible for the fossils’ appearance. So it seems the “hobbits” were their own species, but that leaves still many questions.

The skull of Homo floresiensis.
Image by Ryan Somma via Wikipedia

While the fossils of H. floresiensis are known from between roughly 100,000 and 50,000 years ago (a study a few months ago corrected an earlier inaccurate date of 12,000 years), ancient tools are known on the island back to one million years, so it seems some ancient human species was around there for quite a while, but who?

Not quite 2 million years ago, Homo erectus was the first species of hominin (the human family line) known to leave Africa, and may be our own species’ direct ancestor. Some have suggested that H. erectus, which made it to Indonesia by about 1.5 million years ago, may have also given rise to the tiny Flores species. The other option is that the “hobbits” are descended from a different lineage of hominins that left Africa at a different time, but which we haven’t yet discovered.

A new fossil discovery, published Wednesday, has shed some light on the ancestry of H. floresiensis. These new fossils from Flores date to 700,000 years ago, almost as old as the oldest tools on the island. These new fossils are striking because they look very similar to  H. floresiensis, in shape and also in size! This implies that the small size of the species wasn’t a recent development. Their ancestors appear to have attained their half-meter height shortly after arriving on the island, and remained that way for more than half a million years!

Liang Bua, the cave where the original
H. floresiensis fossils were found.
Photo by Rosino via Wikipedia

What this means for the origin of the dwarf species is still up in the air – the researchers in the new paper suggest that the more ancient species has some features that seem similar to Homo erectus, perhaps supporting the hypothesis that these “hobbits” evolved from that species just as Homo sapiens is thought to have done. But not everyone is convinced that the evidence is clear yet.

On Tuesday, PNAS published an article that discussed how our earliest relatives were surprisingly varied. It is striking that our very recent relatives were also quite varied, and so successful in different forms in different places. Our species really does seem to be the lonely vestige of a long, complex, and fascinating evolutionary lineage. 

References: 

Baab et al. 2016. A Critical Evaluation of the Down Syndrome Diagnosis for LB1, Type Specimen of Homo floresiensis. PLOS One [Link]

Sutikna et al. 2016. Revised Stratigraphy and Chronology for Homo floresiensis at Liang Bua in Indonesia. Nature [Link]

van der Bergh et al. 2016. Homo floresiensis-like fossils from the early Middle Pleistocene of Flores. Nature [Link]

Haile-Selassie et al. 2016. The Pliocene hominin diversity conundrum: Do more fossils mean less clarity? PNAS [Link]