177 Problems with Interpretation: H. floresiensis

Key Idea: The discovery of Homo floresiensis has proved highly controversial with several hypotheses proposed to explain its position in hominin evolution. In 2003, hominin fossils, including an almost complete skeleton, were discovered on the island of Flores, Indonesia. The fossils were assigned to a new species, Homo floresiensis, thought to have lived on the island as recently as 18,000 years ago. However, revised dates in 2016 indicate that H. floresiensis lived ~190,000-50,000 years ago. The new date is close to the time that modern humans reached the area, suggesting that encounter with H. sapiens may have contributed to the demise of the Flores population.

Homo floresiensis was very small and fully bipedal. Although the brain was very small, its organisation was advanced and stone tools associated with the skeleton indicated well established hunting technology. In contrast to these features, aspects of the skeleton showed primitive features found only in apes and early hominins. H. floresiensis probably lived 190,000 to 50,000 years ago. Its discovery caused widespread controversy and several opposing hypotheses were put forward to explain its place in human evolution. Since its discovery, earlier fossils dating to 700,000 years old have been found.

The fossils were discovered in Liang Bua, a limestone cave on Flores Island, Indonesia. The cave contains 12 m of stratified deposits. The remains of modern humans, as well as Homo floresiensis, have been found in the cave.

Rosino

Different interpretations of the fossils

The discovery of Homo floresiensis caused a storm of controversy, not helped by the fact that the specimens were removed from their repository by one palaeontologist, kept from other scientists for three months, and returned damaged. The Indonesian government also denied scientists access to the cave where the fossils were found for two years. Several hypotheses were eventually put forward to explain how such a small statured hominin evolved or survived. These included:

` H. floresiensis evolved a result of island dwarfism. Island dwarfism is a relatively common occurrence where large animals become smaller over time when isolated, e.g. the extinct pygmy elephants on Flores showed this adaptation. ` H. floresiensis is not a new species but instead an individual with a disease or disorder. Some scientists put forward the idea that the small skull was a result of microcephaly, a neurodevelopment disorder. Others thought that perhaps H. floresiensis suffered from congenital hypothyroidism. ` Detailed examination of the bones showed no overlap with any features expected from individuals with the diseases or disorders listed above. A study of the bones and joints of the arm, shoulder, and lower limbs concluded that H. floresiensis was more similar to early humans and apes than modern humans. Small brain size coupled with more advanced brain organisation indicate possible parallel evolution of sapiens-like features.

Brain size: Very small, only 380 cc. 3D scans showed expansion of the prefrontal cortex and temporal lobes, brain regions associated with complex thought.

Facial features: Relatively modern dentition, but teeth are large relative to the rest of the skull.

No chin present.

3D

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Homo floresiensis Homo sapiens

1. Explain the effect that the Flores finds had on the hypothesis that hominins continually evolved larger brains and bodies:

2. Describe the different interpretations of the H. floresiensis bones: