A rare disease characterized by small brain and body size but near normal intelligence is caused by mutations in a gene coding for the protein pericentrin, researchers have found.
The scientists speculate that the condition may explain the tiny, hobbitlike people that occupied a remote, Indonesian island about 18,000 years ago—adding fuel to the debate over whether the unusual creatures were a new species or just diseased modern humans.
Pericentrin helps separate chromosomes during cell division, which is needed for growth.
"The whole body loses its capacity to grow, because cell division is so difficult for people with this defect," said study co-author Anita Rauch of the Institute for Human Genetics at the University of Erlangen in Germany.
On average, disease sufferers grow about three feet (a meter) tall and have a brain the size of a three-month-old baby. However, their intelligence is near normal.
People with the defect also exhibit subtle bony anomalies in their hands and wrists, skull asymmetry, small chins, abnormal teeth, and abnormal shoulders, Rauch said.
Mysterious Hobbit
Descriptions of the hobbitlike people match those of modern humans with this genetic defect, Rauch added.
When the hobbit was discovered in 2004 on the Indonesian island of Flores, scientists hailed it as a new species: Homo floresiensis.
Since then, scientists have debated whether the hobbit is indeed a new species or a modern human with a genetic disease that causes small brains called microcephaly.
The new study links the genetic mutations to a type of microcephaly that limits all growth—that of the brain and the body.
"We think it is very likely that Homo floresiensis indeed had a pericentrin mutation," Rauch said.
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