The Strange Animals of Flores: Homo floresiensis and Its Island World

In 2003, a team of Indonesian and Australian researchers digging in Liang Bua, a limestone cave in western Flores, found the partial skeleton of a tiny adult human. Catalogued as LB1, she stood about 1.06 metres tall and had a brain of roughly 420 cubic centimetres, about the size of a chimpanzee's. The species was named Homo floresiensis.

The same layers held a whole community of unusual animals. The animals of Flores help explain how a small-brained human could survive on an isolated island for hundreds of thousands of years, and why it disappeared.

An island cut off by deep water

Flores lies east of the Wallace Line, a deep-water boundary between the islands of Bali and Lombok and between Borneo and Sulawesi. Even when Ice Age sea levels fell by more than 100 metres, Flores was never joined to mainland Asia.

That shapes everything about its wildlife. Animals could only arrive by swimming, floating on vegetation, or flying. Elephants and their relatives are strong swimmers, rodents raft well, and birds and lizards cross water easily. Large cats, dogs, deer and apes never made it. The result is a short, strange list of species, and a human population that somehow crossed the sea too.

The animals of Flores and the island rule

On islands, large animals often evolve smaller bodies and small animals larger ones. Biologists call this the island rule, and Flores shows both directions at once. The same process produced the dwarf elephants of Sicily.

Two waves of island animals

The Flores fossil record runs back more than a million years. At sites in the So'a Basin, in the centre of the island, the older fauna includes the pygmy Stegodon sondaari, giant tortoises and Komodo dragons. Stone tools at Wolo Sege date to at least 1 million years ago, showing that hominins had arrived by then.

Later, a larger elephant relative, Stegodon florensis, appears. At Mata Menge, about 700,000 years ago, its bones lie with stone tools and with a jaw fragment and teeth of a small hominin, described by Gerrit van den Bergh and colleagues in 2016. A tiny arm bone from the same site, published in 2024, suggests these early Flores hominins were already as small as LB1, or even slightly smaller. Over time the Stegodon line shrank again, into the dwarf form found at Liang Bua.

Hunting the dwarf elephants

At Liang Bua, Stegodon bones are common in the layers with Homo floresiensis and its stone tools. Many come from young animals, and some carry cut marks. A metre-tall hunter with a chimp-sized brain was probably targeting calves, or scavenging carcasses, rather than tackling adults.

Either way, it shows that small brains were no barrier to complex behaviour. The hobbits made stone tools, butchered large prey and lived for tens of thousands of years in an environment shared with large predatory lizards.

Dragons, storks and vultures

Flores had no lions or leopards. Its top predators were reptiles and birds.

The Komodo dragon is the biggest. A 2009 study by Scott Hocknull and colleagues showed that the species evolved in Australia and reached Flores by about 900,000 years ago. Komodo dragons are not island giants, then, but survivors of a group of large Australasian monitors. They still live on the west coast of Flores today. A smaller extinct monitor, Varanus hooijeri, is also known from Flores cave deposits.

The giant marabou stork, Leptoptilos robustus, was described from Liang Bua in 2010 by Hanneke Meijer and Rokus Awe Due. It stood about 1.8 metres tall and weighed around 16 kilograms. Its thick leg bones first suggested it was flightless, but wing bones described in 2022 indicate it could probably fly. Modern marabou storks eat carrion and small animals. Whether the giant stork ever took young hobbits is speculation. No fossil shows it.

An Old World vulture also lived on Flores, a scavenger that likely fed on Stegodon carcasses. When the elephants disappeared, it seems to have gone with them.

Rats as a climate record

Rat bones are the most abundant fossils at Liang Bua. The Flores giant rat, Papagomys armandvillei, is still alive and much larger than a brown rat. Extinct relatives such as Spelaeomys florensis lived alongside it.

Because different rat species prefer open grassland or closed forest, shifts in which rats are common track changes in the landscape. Analyses of the Liang Bua rats suggest the area became less open after about 60,000 years ago. That matters, because a loss of open habitat may have affected the large grazing and browsing animals the hobbits depended on.

They vanished together

In 2016, Thomas Sutikna and colleagues revised the Liang Bua timeline. Homo floresiensis skeletal remains date to between about 100,000 and 60,000 years ago, and stone tools made by the species to between about 190,000 and 50,000 years ago. The dwarf Stegodon, the giant stork and the vulture also drop out of the record around 50,000 years ago.

What caused this is unknown. Candidate explanations include a volcanic eruption, changes in climate and habitat, and the arrival of Homo sapiens, which reached the region by about that time. Some later evidence of fire and different stone tools at Liang Bua may mark modern humans around 46,000 years ago, but that interpretation is tentative.

Why it matters

Flores is a natural experiment in evolution. Given isolation and time, it remodelled elephants, rats, birds and probably humans in unexpected ways. A similar story may have played out on Luzon in the Philippines (see Homo luzonensis). To place the hobbit among other human species, compare it with Homo erectus or explore the interactive family tree.