Researchers have discovered the first human fossils on the Indonesian island of Flores, providing a better understanding of Homo floresiensis, the mysterious “hobbits” of Flores. The new findings, dated to 700,000 years ago, include the smallest arm bone ever found, supporting the theory that the early hominins isolated on the island had greatly reduced body size.
Discovery of early human fossils on the island of Flores
The discovery of extremely rare early human fossils, including a surprisingly small bone belonging to an adult, on the Indonesian island of Flores is reported in a paper published today (August 6) in the journal Nature Communications.
New finds, some 700,000 years old, shed light on the evolution of Homo floresiensis, the so-called “hobbits” of Flores, whose remains were discovered in Liang Bua Cave in the west of the island in 2003 by a team led by Australian-New Zealand archaeologist Professor Mike Morewood (1950-2013).
Archaeological evidence suggests that these diminutive humans with small brains lived in Liang-Boa as early as 50,000 years ago, at a time when our species (Homo sapiens) had long inhabited southern Australia.
“Theories about the origin of the Hobbits
There has been much debate about the origin of the mysterious people of Flores. At first, it was assumed that Homo floresiensis were a dwarf descendant of the early Asian Homo erectus.
Another theory is that the “hobbit” is a late remnant of an ancient hominid that preceded Homo erectus in Africa and was originally short; in this case, Homo habilis or the famous “Lucy” (Australopithecus afarensis) are likely candidates.
Fossils from Mata Menge
Besides Liang Bua, hominin fossils have only been found at one other site on Flores: the exposed site of Mata Menge, 75 km east of the cave. Located in the sparsely populated tropical grasslands of the Soa Basin, this site had previously yielded a few hominin fossils (a jaw fragment and six teeth) excavated from a sandstone layer exposed by a small stream around 700,000 years ago.
The fossils from the Mata Menge hominins at Liang Bua, dating to 650,000 years ago, belong to at least three individuals whose jaws and teeth were slightly smaller than those of Homo floresiensis, suggesting that small body size emerged early in the history of flora hominins.
However, because fossils from this region lack postcranial elements (bones from the lower part of the head), it could not be confirmed that these hominins from the Soa River Basin were at least as small, if not slightly smaller, than Homo floresiensis.
The species to which the fossils from Mata Menge belonged was also uncertain due to the lack of further diagnostic specimens. However, some of the teeth were thought to be intermediate in shape between those of early Asian Homo erectus and Homo floresiensis.
New data from recent excavations
The new study, published in the journal Nature Communications, was led by Professor Yusuke Kaifu from the University of Tokyo, Ivan Kurniawan from the Indonesian Geological Survey, and Associate Professor Gerrit van den Bergh from the University of Wollongong.
Three more hominin fossils dated to 700,000 years ago were reportedly discovered at Mata Menge after several seasons of excavations at the site. Most importantly, the new collection includes the first postcranial element, the distal shaft of the adult humerus (lower half of the forearm).
The importance of new fossil findings
The discovery of a fossil limb bone from the Mata Menge site was highly anticipated because it contains rich evidence for the ancestral origin of Homo floresiensis.
Digital microscopy of the microstructure shows that the small arm bone belongs to an adult. Based on the estimated length of the bone, the team was able to calculate that this hominin was about 100 cm tall. This is about 6 cm shorter than the estimated height of the 60,000-year-old Homo floresiensis skeleton from Liang Bua (~106 cm, based on femur length).
“Not only is this 700,000-year-old adult humerus shorter than that of Homo floresiensis, it is also the smallest humerus known from a hominin fossil anywhere in the world,” said Professor Adam Brumm, from Griffith University’s Australian Research Centre for Human Evolution, co-author of the paper.
“This very rare specimen supports our hypothesis that the ancestors of Homo floresiensis were extremely small in body size; however, given the very small proportions of this limb bone, it is now clear that the early ‘hobbit’ ancestors were much smaller than we previously thought.”
Source: Port Altele
