IN A hole in the ground there lived a hobbit. Or should that be: in a hole in the ground there lived a pygmy human with microcephaly? According to a study of dwarfing in a range of mammals, the supposed new species Homo floresiensis announced in 2004 was in fact a modern human with a pathological condition.
The hole, a limestone cave on the island of Flores, Indonesia, contained the remains of a tiny female, apparently a new species of early human. Named H. floresiensis by the discoverers, she quickly became known as 鈥渢he hobbit鈥�. However, when the find was reported (快猫短视频, 30 October 2004, p 8) some anthropologists disputed whether it really was a new species, arguing that the skeleton had characteristics of a modern human with microcephaly, a condition that causes an abnormally small cranium.
The hobbit鈥檚 discoverers, Peter Brown and Mike Morwood from the University of New England in Australia, proposed that the 1-metre-tall specimen (known as LB1) derived from an isolated population of Homo erectus that dwarfed to cope with the restricted diet on the island. Yet at 380 cubic centimetres, some thought that LB1鈥檚 cranial capacity was too small for it to be a dwarf H. erectus. Brown and Morwood disputed this, but their conclusion has now been challenged again.
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鈥淎s they dwarf, species鈥� brain sizes decline far more slowly than body size,鈥� says Ann MacLarnon from Roehampton University, UK. She and a team from the Field Museum in Chicago have modelled dwarfing in a range of mammals from dogs to elephants, and they calculate that the body of a dwarfed H. erectus with a 400-cc brain would weigh just 2 kilograms. 鈥淭hat鈥檚 one-tenth of what the Flores people must have weighed,鈥� MacLarnon explains. The team believes the only explanation for the discrepancy is microcephaly (Science, DOI: 10.1126/science.1121144).
鈥淩esearchers calculate that the body of a dwarfed H. erectus with a 400-cc brain would weigh just 2 kilograms鈥�
鈥淚t鈥檚 perfectly plausible that these were pygmy people. But there鈥檚 only one skull, and that is human and microcephalic,鈥� says Field Museum team leader Robert Martin. 鈥淭hese were sophisticated people, with a high level of mental development. Not only could they make fine tools, they could also care for a microcephalic,鈥� he says.
鈥淚t鈥檚 perfectly plausible that these were pygmy people. But there鈥檚 only one skull, and that is human and microcephalic鈥�
Morwood describes the microcephaly explanation as bizarre. 鈥淎lthough we only have one cranium, the other bones we found show that LB1 was a normal member of an endemically dwarfed hominid population,鈥� he says. The reduced body mass and brain size and short, thick legs mirror traits in other island populations of large mammals, Morwood says. The microcephaly theory ignores other evidence from the cave, he adds.
