'The Hobbits' of Flores: Fossils shed light on mysterious island-dwelling ancestors of man

The ancestors of 'Hobbits' appear to have been discovered in Indonesia. 700,000-year-old fossils discovered on the island of Flores may shed a light on the origins of the early human species Homo Floresiensis – sometimes nicknamed as Hobbits because of their small stature. The discovery suggests the species may be descending from Homo Erectus, rather than from smaller and more primitive groups of humans, scientists have said.

In 2004, scientists discovered on the little Indonesian island of Flores the bones of tiny hominins (estimated height of 1.06m or 3ft 6in)who would have lived there 50 000 years ago. It would not have been more than a metre tall, with shrugged-forward shoulders, small brains and large feet. The name Hobbit came as a result of its similarity with the fictional JRR Tolkein characters.

Since their, scientists have been divided over Homo Floresiensis' possible origins and how they got to be so small.

The latest research on Flores describes the fossilised teeth and mandible fragment of at least three small humans, a discovery which could reveal some of Homo Floresiensis' secrets. In their two papers, published in the journal Nature, the researchers suggest these fossils are that of the Hobbits' ancestors, and pave the way to understanding their history.

Descending from Homo Erectus

Up until now, there had been two conflicting hypothesis about where Homo Floresiensis came from. The fact they were so small led many to believe the species descended from ancient, more archaic groups of humans, like Australopithecus.

However, some scientists pointed out its ability to create small stone tools and some of its morphological features suggested it was maybe more closely related to early Asian Homo Erectus. In this scenario though, the Hobbit would represent a striking case of evolutionary reversal, as its body and brain size would have shrunk compared with Homo Erectus.

The new fossils – six teeth and a mandible fragment – were excavated in 2014 along with other animal fossils in the upper part of a fluvial sandstone layer, at the site of Mata Menge, 50km away from where the "hobbits" were found a decade before. Four different dating methods confirmed that they were 650,000 years older than the "Hobbit fossils".

Although the teeth looked smaller in size than that of Homo Floresiensis, CT scans and in-depth morphological analysis revealed that they belonged to an Homo Floresiensis-like adults. More importantly, the fossils displayed striking similarities with Homo Erectus' teeth, but not with Australopithecus' or Homo Habilis'.

"We believe these fossils are that of Homo Floresiensis ancestors, and that they descended from Homo Erectus. We would have expected them to be bigger, closer in size to Homo Erectus, but it seems that they developed their small size very early on, from 700,000 years ago. They were in fact kind of a Homo Erectus dwarf", researcher Gerrit van den Bergh said during a press conference.

To confirm these findings, the researcher will need to look for more ancient hobbit fossils, especially postcrania fossils, to compare morphological features more precisely. Genetic analysis will however be impossible, as the wet and tropical climate has made any recovery of DNA impossible.

Island life

Although these fossils may solve the mystery of Homo Floresiensis' origins and ancestry, the scientists are not yet sure what caused the little "Hobbits" to develop such a small size – so much smaller than their Homo Erectus ancestors.

A key hypothesis is that this is the result long-term isolation on a small island, with limited food resources and a lack of predators. Extinct dwarf elephants fossils recovered during excavations on Flores showed the same adaptation.

Though the cause of their arrival on Flores will probably never be known, Gerrit van den Bergh speculates that potential "freak events" – like tsunamis – may have brought humans progressively to the island over thousands of years.