An international team of archeologists and other researchers on the Indonesian island of Flores found new fossils that belong to extremely rare early human species. Homo floresiensis has been likened by scientists to the Hobbits from JRR Tolkien’s The Lord of the Rings series due to their small stature. The three roughly 700,000 year-old bones shed light on the evolution of Homo floresiensis, or the ‘Hobbits’ of Flores.
These newly discovered fossils are detailed in a study published August 6 in the journal Nature Communications and include the first bones from below the head of one of these hominins.
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Animals of unusual size
A small species of humans makes some scientific sense in Indonesia, as it is known for non-human animals of unusual size. Small-bodied elephant relatives called Stegodons, giant 15 pound rats, enormous crocodiles, and more all once roamed this bevy of biodiversity.
Evidence of these early humans were first uncovered in 2003, at Liang Bua cave by a team co-led by the late archaeologist Mike Morwood. Archaeological evidence suggests that humans stood at only about 3.4 feet tall, had small brains, and lived as recently as 50,000 years ago. At this time, Homo sapiens was long established to the south in Australia.
However, there is still considerable debate about how these hominins in Southeast Asia evolved to be so small, as well as their origin. Some have hypothesized that Homo floresiensis was a smaller descendant of early Asian Homo erectus. Another theory is that they are a late-surviving remnant of a more ancient hominin species from Africa that predates Homo erectus. If this is the case, it could also have been a descendant of Homo habilis or the infamous and super-strong “Lucy” (Australopithecus afarensis).
When did they get to be so small?
The fossils in this new study were found further away from the Liang Bua cave, in Mata Menge. This open-air site is about 46 miles east of the cave in sparsely populated tropical grasslands of the So’a Basin. Previously, archaeologists have found several hominin fossils there, including a jaw fragment and six teeth from a layer of sandstone that was laid down by a small stream about 700,000 years ago.
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The new fossils also pre-date the Liang Bua hominins by about 650,000 years. They belong to at least three individuals who possibly had even slightly smaller jaws and teeth than the original Homo floresiensis specimens, implying the Flores hominins evolved their small body size early on.
However, there was still an important piece of the puzzle missing during previous excavations at Meta Menge. The postcranial elements–bones from below the head–from this species had yet to be uncovered. Without these, it couldn’t be confirmed that these hominins were at least as small as, if not smaller than Homo floresiensis.
Some critical bones
Importantly, the team on this study found the first postcranial element belonging to Homo floresiensis. They uncovered a distal shaft of an adult humerus–or the lower half of the upper arm bone.
Digital microscopy of fossils indicate that the small humerus belonged to an adult. The team was able to use the bone length to calculate the body height, and believe it was about 3.2-feet-tall. This is roughly two inches shorter than the estimated body length of the 60,000-year-old Homo floresiensis skeleton found in the Liang Bua cave (roughly 3.4-feet-tall).
“This 700,000-year-old adult humerus is not just shorter than that of Homo floresiensis, it is the smallest upper arm bone known from the hominin fossil record worldwide,” Adam Brumm, a study co-author and archeologist at Griffith University in Australia, said in a statement. “This very rare specimen confirms our hypothesis that the ancestors of Homo floresiensis were extremely small in body size; however, it is now apparent from the tiny proportions of this limb bone that the early progenitors of the ‘Hobbit’ were even smaller than we had previously thought.”
The two teeth from Mata Menge are also small in size. One of them also has similar shape characteristics that are most consistent with early Homo erectus from the island of Java. However, this similarity does not support the hypothesis that Homo floresiensis evolved from an earlier and more primitive type of hominin.
More digs into the fossil record are needed to piece together the larger story of this small group of human relatives.
“The evolutionary history of the Flores hominins is still largely unknown,” said Brumm. “However, the new fossils strongly suggest that the ‘Hobbit’ story did indeed begin when a group of the early Asian hominins known as Homo erectus somehow became isolated on this remote Indonesian island, perhaps one million years ago, and underwent a dramatic body size reduction over time”.
