When researchers discovered fossilized shards of a rod-shaped bone 3-1/2 inches (88 mm) long at Mata Menge on Indonesia’s Flores island, they were initially bagged and labeled “crocodile bone fragment?” It was only after that they learned who they truly were.
These remnants of the upper arm bone, known as the humerus, date back around 700,000 years and represent the tiniest limb bone known for any member of the human evolutionary lineage – an adult individual of the minuscule extinct species Homo floresiensis. And t
The fossil has solved the puzzle of the origins of this animal, dubbed “The Hobbit.”
Scientists revealed on Tuesday the finding of this partial humerus, which is missing both ends, as well as two fossilized teeth from Mata Menge in Flores’ So’a Basin, where the volcano Ebulobo towers over the landscape. While teeth and jaw fossils of the same age were previously discovered at the site, the humerus is the first Hobbit bone discovered beyond the cranium at Mata Menge.
Based on the size of the bone, the researchers concluded the individual stood about 3 feet 3 inches (one meter) tall, which is about three inches (6 cm) shorter than the estimated height of the famous 60,000-year-old Homo floresiensis fossil discovered in 2003 at the Liang Bua cave site, about 50 miles (75 kilometers) away.
Since the dramatic discovery of Homo floresiensis, scientists have questioned its origins. The major hypotheses were that the Hobbit descended from either an archaic human species known as Homo erectus, which developed in Africa and dispersed to other areas of the world, or from even more primordial species such as Homo habilis or Australopithecus afarensis, neither of which is known to have left Africa.
The similarities between the Mata Menge fossils and Homo erectus fossils from the Indonesian island of Java provide significant evidence that Homo floresiensis originated from that species, according to the researchers.
“This means that Homo floresiensis experienced dramatic body size reduction from large-bodied Homo erectus, whose body size was similar to us modern humans,” said University of Tokyo paleoanthropology professor Yousuke Kaifu, lead author of the study published in Nature Communications.
According to Kaifu, the Flores fossils are most comparable to Homo erectus fossils found in Sangiran, Java, dated from 1.1 million to 800,000 years ago, rather than the more primitive species.
“The discovery offers support to the idea that an evolutionary process known as island dwarfism tinkered with the genetics of a group of large-bodied Homo erectus that somehow made it from the continental landmass of Asia to the isolated island of Flores, perhaps one million years ago or more,” said archaeology professor and study co-author Adam Brumm of Griffith University’s Australian Research Centre for Human Evolution.
They lowered their body size dramatically on Flores between one million and 700,000 years ago, giving rise to Homo floresiensis, Brumm added.
Larger-bodied creatures, such as elephants, who lived on Flores, grew smaller over time due to the island effect.
“It is believed that the primary reason for this size reduction over many generations is because being little has more advantages than being large on an island. Gerrit van den Bergh, a paleontology professor at the University of Wollongong and research co-author, believes that periodic food shortages are the most plausible selecting mechanism driving lower body size.
Homo erectus initially arose about 1.9 million years ago, with physical proportions similar to our own but a smaller brain.
The original length of the Mata Menge humerus, discovered in 2013 and properly recognized in 2015, was approximately 7.9-8.3 inches. This compared to the later Liang Bua Hobbit’s 9.6 inches (243 mm) and a modern-day average of roughly 11.8 inches (299 mm).
“I first thought that the tiny humerus could be a child,” Kaifu told me.
A microscopic analysis of the Mata Menge humerus found indications of bone remodeling, indicating that it was from an adult.
Ten Homo floresiensis fossils, including several described in 2016, from at least four individuals – two adults and two children – were discovered in sandstone in Mata Menge, together with stone tools. The fossils indicate that these Homo floresiensis ancestors were slightly smaller than the later Hobbits.
Homo floresiensis became extinct shortly after our species arrived in the region.
“I think our species very likely was the culprit,” Brumm told me. “This unique lineage of archaic hominins appears to have existed on Flores for an extremely long time, and then it vanishes shortly after Homo sapiens is known to have established a foothold in the area. “That doesn’t seem like a coincidence.”
