A study on rats gives a snapshot of the hominid's habitat 'Hobbit'.

A study of the size of the rat body evolving over time gives a glimpse of the habitat of the mysterious hominin Homo floresiensis – nicknamed the "Hobbit" because of its small size.

the Journal of Human Evolution publishes this study, based on an badysis of thousands of rodent bones, mainly anterior and posterior limbs, from an Indonesian cave where H. floresiensis was discovered in 2003. The results indicate that the local habitat consisted mainly of open grbadlands more than 100,000 years ago, but began to move rapidly to a more closed environment 60,000 years ago.

"Our article is the first one we know to use rat foot bones in this way to interpret ecological changes over time." It provides new evidence for the local environment at the time of 39 Homo Floresiensis, "says Elizabeth Grace Veatch, PhD candidate at Emory University and first author of the study.

H. floresiensis was only 3 feet 6 inches and was known to have lived about 190,000 to 50,000 years ago on the oceanic island of Flores, in eastern Indonesia. The little hominin shared the island with animals that could come from the pages of a Tolkien novel, including giant Komodo dragons, six-foot tall storks, six-footed vultures. feet and dwarf stegodons, herbivores resembling elephants with oversized and diving defenses.

It is the rats, however, that interest Veatch the most.

The Murids, as it is called in the rat family, are more taxonomically diverse than any other group of mammals and are found in almost every region of the world. "They present an incredible range of behaviors that occupy many different ecological niches," Veatch said. "And because small mammals are generally sensitive to ecological change, they can tell you a lot about what's happening in an environment."

The study was based on remains of the limestone cave known as Liang Bua, where partial skeletons of H. floresiensis have been discovered, as well as stone tools and animal remains – mostly rats. In fact, of the 275,000 animal bones identified in the cave up to now, 80% come from rodents.

Veatch came to Emory to work with paleoanthropologist Jessica Thompson, a leading expert in the use of taphonomy – the study of what happens to bones after the death of an organism – to learn more on the evolution of human nutrition. Although Thompson has now moved to Yale University, she continues to advise Veatch in her graduate studies at Emory.

Veatch joined the Liang Bua project by completing an internship with the Human Origins program at the Smithsonian Institution's National Museum of Natural History. His mentor at this location was the paleoanthropologist Matthew Tocheri (now working at Lakehead University in Ontario), who shares the first author of the current paper with Veatch.

"Matthew asked me if I wanted to badyze rat bones and I replied:" Sure, "Veatch remembers." I had no idea what I was going to do. ; getting into. "

The study focused on about 10,000 rat bones Liang Bua. The remains covered five species of different sizes, from Rattus hainaldi the size of a papagomys armandvillei mouse the size of a cat, known as the giant Flores rat. After categorizing the bones, the researchers were able to badociate them directly with species and types of environment.

While rats can adapt to new environments, the morphologies of different species tend to adapt to their preferred environment. For example, the habitat of Komodomys rintjanus of medium size, included in the study, consists mainly of intermittent open grbadlands with patches of forest. On the other hand, R. hainaldi and P. armandvillei, two giants, prefer more closed or semi-closed forest habitats.

Monitoring the relative abundance of different species of rats over time indicated that the local ecology consisted mainly of open grbadlands 100,000 years ago, moving to a more closed forest habitat, there is about 60,000 years old. It was around the same time as skeletal Homo floresiensis, the Pygmy Stegodon, the giant storks, the vulture and the Komodo dragons disappear from Liang Bua.

"The evidence suggests that Homo floresiensis Perhaps they have preferred more open habitats where they may have been part of this trellis guild of stegodons, storks and vultures, "says Veatch. We think that when the habitat has changed, it becomes more wooded, Homo floresiensis probably left the Liang Bua area, tracking these animals to more open habitats elsewhere on the island. "

Many more mysteries remain concerning H. floresiensis, Says Veatch, and Liang Bua's rat bones can help solve some of them.

A key question is whether H. floresiensis hunted small game.

"Our early ancestors adapted to the consumption of large quantities of big game, whether by hunting or cleaning – or both," said Veatch. "Big game has undoubtedly become an essential food source, leading to many social and physiological adaptations, including social cooperation and brain expansion, but much less is known about the role of small game hunting. play in our first everything. "

Liang Bua, she says, offers an ideal opportunity to study what a low-brained hominin is like H. floresiensis, could hunt if he had both big game sources, such as Stegodon, and small game, like the giant Flores rat and other species of rats.

Veatch is currently conducting studies at the Liang Bua site, including experiments to determine the difficulty of capturing Flores wild rats. She is also doing research at the ARKENAS (Pusat Penelitian Arkeologi Nasional) museum in the Indonesian capital Jakarta, where many bones from the cave are now stored. She badyzes a large sample of bones to determine if some have cut marks – indicating tool-killing – or stung marks that would indicate that they have been digested by owls or other raptors that may have deposited them in the cave.

"In Indonesia, my nickname is Miss Tikus, which means" Miss Rat, "said Veatch." That suits me perfectly because rats are really intelligent and extraordinary animals. We see them throughout the sequence of Liang Bua's archeology and we will continue to use them in future studies to find out more about what happened in the cave. . "