Discovery locations of Javanese Homo erectus and Homo floresiensis . Areas of land exposed by falling sea levels during the glacial period are shown in gray. CREDIT: Map made by Yousuke Kaifu with GeoMapApp (www.geomapapp.org)/CC BY.
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 predatesHomo erectus. If this is the case, it could also have been a descendant ofHomo 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.
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.
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).
The distal humerus fragment, excavated in 2013 at the site Mata Menge. CREDIT: Yousuke Kaifu
“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 erectusfrom 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.
“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”.
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