A second skull would be especially helpful. Critics of the new species theory have latched onto the Hobbit's measly 400-cubic-centimeter brain as a sure sign of an abnormality called microcephaly in which the brain does not reach normal size. Some prominent advocates of a human Hobbit say that a second skull could settle the debate. "It's the acid test," says primatologist Robert Martin of the Field Museum in Chicago, who contends that the existing Hobbit skull is a malformed human skull. If he is correct, a second skull would be closer to 1,000 cubic centimeters, he says.
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Some other holdouts against the separate species view say the question is less straightforward. "Reopening the cave is great and I am confident that the investigators will find more material similar to that already recovered," says evolutionary biologist Gary Richards of the University of California, Berkeley, who has argued that the Hobbit represents a dwarfed—but healthy—human. "Unlike others, I am of the opinion that this will not confirm that the remains are a [new] species."
Hawks also thinks that a similar second skull would seal the deal for a new species. I tend to side with the other skeptics, in that one needs to -- and this is a logical preference on my part, btw, not a statement of how things are -- establish that these critters exhibit traits well outside expected variation. That would mean demonstrating that inheritance of these characteristics among a relatively isolated population is highly unlikely.