Two recently discovered small hominin species, Homo floresiensis and Homo luzonensisraises the question of why such extreme body size reduction occurred in extinct human species in island environments. Previous research at Mata Menge on the Indonesian island of Flores has shown that early Middle Pleistocene human ancestors Homo floresiensis The jaws and teeth were even smaller. Now, paleoanthropologists have discovered additional hominid fossils in the same deposits at Mata Menge. The adult humerus (the lower half of the upper arm bone) is estimated to be 9 to 16 percent shorter and thinner than the type specimen. Homo floresiensis It is estimated to be about 60,000 years old and is smaller than the humerus of an adult human from the Plio-Pleistocene epoch. Homo floresiensis The lineage probably evolved from early Asia. Homo erectus This was a lineage that had existed for a long time on Flores Island, with a remarkably small body size, for at least 700,000 years.

Homo floresiensis This is a small hominin species from the Late Pleistocene discovered in a limestone cave in Liang Bua, western Flores.

Archaeological evidence suggests that this species lived in Liang Bua as recently as 50,000 years ago, around the time that our species first appeared. Homo sapienshas been established in southern Australia for a long time.

The origins of the mysterious humans from Flores have been much debated.

The first hypothesis was Homo floresiensis They were dwarf descendants of early Asians Homo erectus.

Another theory is that “Hobbits” are remnants of an earlier human race that originated in Africa around 1000 BC. Homo erectus If you are naturally short, some good candidates are: Homo habilis or Australopithecus afarensisThis species includes the famous “Lucy”.

Besides Liang Bua, hominin fossils have only been found at one other site on Flores, at the open-air site of Mata Menge, 75 km east of the cave.

Located in the sparsely populated tropical grasslands of the Soa Basin, the site has previously contained several other hominin fossils, including a jaw fragment and six teeth, unearthed in sandstone deposits near a stream some 700,000 years ago.

The Mata Menge fossils are 650,000 years older than the Liang Bua man and have been found to belong to at least three individuals, with jaws and teeth slightly smaller than those of the Liang Bua man. Homo floresiensisThis suggests that small body sizes evolved early in human history on Flores.

However, because no bones below the skull have been found in the fossil record from this site, it is not possible to confirm whether these Soar Basin hominins were at least as large, or even slightly smaller. Homo floresiensis.

Furthermore, due to a lack of diagnostic specimens, it was unclear to which species the Mata Menge fossils belonged.

However, some of the teeth are thought to be intermediate in morphology to earlier Asian teeth. Homo erectus and Homo floresiensis.

This is an artist's reproduction Homo erectusImage courtesy of Yale University.

in New paper Published in the journal Nature CommunicationsProfessor Yosuke Kaifu of the University of Tokyo and his colleagues report the discovery of three additional hominin fossils at the 700,000-year-old Mata Menge site after several on-site excavations at the site.

Most importantly, this new assemblage contains the first postcranial element, the distal shaft of the adult humerus.

The fossil limb bones discovered at the Mata Menge excavation site have been long awaited as they provide a wealth of evidence regarding the origins of our human ancestors. Homo floresiensis.

Digital microscopic examination of the microstructure revealed that the small humerus belonged to an adult individual.

Based on the estimated length of the bones, the team was able to calculate that the hominin was about 100 centimetres tall.

This is about 6cm shorter than the estimated height 60,000 years ago. Homo floresiensis Liang Bua skeleton (approximately 106cm based on femur length).

“This 700,000-year-old adult humerus is Homo floresiensis“This is the smallest humerus bone in the human fossil record anywhere in the world,” Professor Adam Blum, from Griffith University, said.

“This extremely rare specimen Homo floresiensis The body size was very small.”

“But the small size of these limb bones reveals that the hobbit's early ancestors were even smaller than we previously thought.”

Two additional hominid teeth from Mata Menge are also smaller in size, one of which is an early Homo erectus Java.

This similarity is Homo floresiensis It evolved from an older, more primitive type of hominin and has never been found anywhere else, not even in Indonesia, or anywhere else in Africa.

The Mata Menge skeleton now contains a total of 10 fossil specimens, representing at least four individuals, including two children.

They are all anatomically very similar to the Liang Bu. Homo floresiensis They are now considered to be an ancient variant of this human species.

However, this early form, although directly ancestral to the “hobbits”, had a less specialized dentition (more primitive teeth) than the descendants of Liang Bua.

Furthermore, the small arm bones indicate that extreme body size reduction occurred early in the history of Flores's population.

“The evolutionary history of humans on Flores is still largely unknown,” Professor Blum said.

“But the new fossils suggest that the story of The Hobbit Homo erectus “Maybe a million years ago, it somehow became isolated on this remote Indonesian island, and over time its body size dramatically decreased.”

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Hiroyuki Kaifu others2024. Early evolution of small body size Homo floresiensis. Nat Community 15, 6381; doi: 10.1038/s41467-024-50649-7