Researchers have hotly debated whether the 18,000-year-old Hobbit remains, found on the Indonesian island of Flores, represent a new species or a human dwarf with a pathologically small brain. Much of the debate has centered on the single Hobbit skull found so far, part of a specimen called LB1. Unfortunately, researchers have no hard and fast criteria for microcephaly, an umbrella term for conditions that stunt brain growth at ages four or five, says paleoanthropologist Dean Falk of Florida State University.
So Falk and her colleagues at the Washington University School of Medicine in St. Louis created virtual skull casts from nine human cases of microcephaly to identify criteria for ruling LB1 in or out. The brains of the microcephalics tend to be narrow in front and protrude in the back, the group reports in this week's Proceedings of the National Academy of Sciences USA.
The team used two measurements of these brain dimensions to distinguish the nine microcephalics from an additional sample of 10 normal human skull casts. Most notably, using these measurements, the Hobbit skull fit in with the normal ones, suggesting it is not diseased, Falk says. "We worked so hard to do a meticulous, well-designed scientific study," she says, adding that the microcephaly interpretation of LB1 is "not even a reasonable hypothesis anymore."
Falk says that competing research groups are nonetheless still skeptical, and finding a new skull at Liang Bua might be the only way to finally quell the debate. "Let's hope they find more," she says.