News & Views item - May 2006

 

 

Further Revelations and Discussion About Homo floresiensis ... those Hobbits). (May 19, 2006)

    While paleoanthropologist Robert D. Martin of the Field Museum of Natural History in Chicago, Illinois, and his colleagues continue to challenge that Homo floresiensis was a normal if diminutive primitive human, they are backtracking a bit from their earlier suggestion that the Hobbit suffered from microcephaly.  Martin told Science's Elizabeth Culotta "'I'm not saying I'm 100% certain it's microcephaly; I'm saying that that brain size is simply too small' to be normal."

Details of the H. floresiensis skeleton suggest that it may be descended from H. erectus.
Credit: Science/Susan Larson

 

Paleoanthropologist Ralph Holloway of Columbia University, who is also studying microcephalic brains, is more cautious and told Culotta that so far he sees some differences between the Liang Bua skull and what's called primary microcephaly, but he warns that it will take a substantial survey to be sure. "I am coming around to believing that it isn't primary microcephaly," he says. But "I certainly would not rule out pathology just yet."

At a meeting of the Paleoanthropology Society in San Juan, Puerto Rico from April 24-26, anatomists Susan Larson and William Jungers of Stony Brook University in New York reported on their findings upon examining the bones. They had been invited by Michael Morwood of the University of New England, Armidale and Tony Djubiantono of the Indonesian Centre for Archaeology in Jakarta to examine the material.

 Larson described her work on the upper arm bone, or humerus, of the original skeleton. It lacks a feature present in Homo sapiens. As Culotta reports the,

...head of the humerus is twisted with respect to the elbow joint by about 145 to 165 degrees. As a result, when you stand straight, the insides of your elbows face slightly forward, allowing you to bend your elbows and work with your hands in front of your body. ...Larson found that the ...humeral head [of H. floresiensis]  was in fact rotated only about 110 degrees. (No rotation would be expressed as 90 degrees.) Curious, she examined the broken collarbone, plus a shoulder blade from another individual. Larson concluded that the upper arm and shoulder were oriented slightly differently in H. floresiensis than in living people. The shoulder blade was shrugged slightly forward, changing its articulation with the humerus and allowing the small humans to bend their elbows and work with their hands as we do."

When Larson looked at other human fossils for comparison, she found another surprise: The only H. erectus skeleton known, the 1.55-million-year-old "Nariokotome boy" from Kenya, also has a relatively untwisted humerus, a feature not previously noted. Larson concluded that the evolution of the modern shoulder was a two-stage process and that H. erectus and H. floresiensis preserved the first step.

H. erectus expert G. Philip Rightmire of Binghamton University in New York, who works on fossils from Dmanisi, Georgia, supports this view. Larson's and Jungers's analyses "make it clearer and clearer that Homo floresiensis is not some sort of dwarf modern human. This is a different species from us," he says.

Jungers reported more unexpected findings. He found that the orientation of the pelvic blades is modern. The observation adds weight to the notion that hobbits had H. erectus, rather than australopithecine, ancestry.

Certainly there is much still to be done but it looks more probable now that Morwood and his team have discovered an ancient hominid which traces its origins to H. erectus.