Ancestors of Indonesian Hobbits Could Have Been Even Tinier

700,000 years ago, humans lived on an island in Indonesia. Homo floresiensisThe so-called Hobbits lived on the same islands until much more recently, and while newly analyzed fossils may show their ancestors, the evolutionary story of these small-bodied hominins remains shrouded in mystery.

Fossil H. floresiensis Hobbit bones were first discovered in the Liang Bua cave on the island of Flores in 2003. The hobbit bones date back to between 90,000 and 50,000 years ago.

In 2016, Yosuke Kaifu Researchers from the University of Tokyo discovered hominin fossils at Mata Menge, an open-air archaeological site that was once a riverbed on the east side of Flores island. Approximately 700,000 years ago It includes part of a skull, part of a jawbone and six teeth, all of which are unusually small for a hominoid.

That the Mata Menge humans were the ancestors of hobbits was an obvious interpretation, but the fragmentary nature of the remains meant that no certainty was possible.

Kaifu and his colleagues described three new fossils from Mata Menge: two teeth and part of an important upper arm bone. This limb bone “finally allowed us to determine the body size,” Kaifu says.

Unfortunately, the humerus was not complete; it was broken along its shaft. To determine exactly where the bone broke, the team looked for key landmarks, such as grooves that support nerves and muscle attachment points. From these clues, the team determined that the bone broke about halfway through, and estimated its total length to be between 20.6 and 22.6 centimetres.

The bone microstructure shows characteristics that indicate it was from an adult. Using the humerus as a whole-body estimate, the team estimates that the Mata Menge hominin was between 93 and 121 cm tall, with the highest estimate being 100 cm. H. floresiensis The Liang Bua specimen is at least six centimetres tall, Kaifu said, making it the smallest adult hominin ever found.

This discovery H. floresiensis Kaifu says the species has long been suspected to be a descendant of a large species called a hominin. Homo erectus The Mata Menge teeth and the hominoids from the Mata Menge fossils are the first hominid species known to have lived outside of Africa, including on the Indonesian island of Java, about 1 million years ago. “I'm pretty sure they descended from those groups,” Kaifu says. This is based on the Mata Menge teeth and the hominoids from the Mata Menge fossils. Homo erectus From Java and because of the closeness of the date and location.

It has been suggested that a small number of Homo erectus They probably arrived on Flores by chance, where they lived in isolation, and then must have become smaller over the next 300,000 years, Kaifu says. “They were small early on, and they stayed small for a long time after that,” he says.

It's common for island animals to become smaller over the course of evolution because limited food resources and a lack of large predators mean there's no advantage to being large. Along these lines, Flores has been home to generations of dwarf elephants and other species.

But there is another explanation. Debbie Argue Australian National University, Canberra Small Species, Big Mystery: The Story of Homo floresiensis.

Argus said Mata Menge's teeth were: H. floresiensis Liang Bua's molar. For example, Mata Menge's molar has five sharp “cusps” H. floresiensis They have four molars. “There's no clear indication that anyone evolved into anyone else,” she says, and it's not clear why the latter evolved. H. floresiensis It would have evolved a slightly larger body than its ancestors. Homo erectus From the island.”

For these reasons, Argue says we shouldn't assume that the Mata Menge hominins were the ancestors of hobbits: “I would consider an alternative hypothesis, that they are a new, previously unknown species.” If island life could have caused one group of humans to evolve smaller in size, she suggests, it could have happened twice.

In 2017, Argue and his colleagues H. floresiensis Compared to other hominins, the closest known relatives are Homo erectus instead It is called the old species Homo habilisThis is known only from Africa. Based on this, they proposed the following: H. floresiensis It actually evolved in Africa, HabilisSome of them then migrated east, ending up on the island of Flores. Argue says more fossils are probably needed to settle the question of the hobbit's origins.