Diminutive humans whose remains were found on the remote Indonesian island of Flores in 2003 truly are a new species, and not pygmies whose brains had shrivelled with disease, researchers reported Wednesday.
Anthropologists have argued, sometimes bitterly, since the discovery of Homo floresiensis -- dubbed "the hobbit" due to its size -- as to the identity and origins of these distant cave-dwelling cousins.
Measuring about a metre (three feet) and weighing in at 30 kilos (65 pounds), the tiny, tool-making hunters may have roamed the island for which they were named as recently as 8,000 years ago. The fossils are about 18,000 years old.
Many scientists have said H. floresiensis were prehistoric humans descended from homo erectus, stunted by natural selection over millennia through a process called insular dwarfing.
Others countered that even this evolutionary shrinking, well known in island-bound animals, could not account for the hobbit's chimp-sized grey matter of barely more than 400 cubic centimetres, a third the size of a modern human brain.
And how could such a being have been smart enough to craft its own stone tools?
The only plausible explanation, they insisted, was that the handful of specimens found suffered from a genetic disorder resulting in an abnormally small skull or -- a more recent finding -- that they suffered from "dwarf cretinism" caused by deficient thyroids.
Two new studies in the British journal Nature go a long way toward settling this debate, even as they raise new quandaries that are sure to stoke further controversy.
A team led by William Jungers of the Stony Brook University in New York tackled the problem from the other end by analysing the hobbit's foot.
In some ways it is very human. The big toe is aligned with the others and the joints make it possible to extend the toes as the body's full weight falls on the foot, attributes not found in great apes.
But, in other respects, it is startlingly primitive: far longer than its modern human equivalent, and equipped with a very small big toe, long, curved lateral toes, and a weight-bearing structure closer to a chimpanzee's.
Recent archeological evidence from Kenya shows that the modern foot evolved more than 1.5 million years ago, most likely in Homo erectus.
So unless the Flores hobbits became more primitive over time -- a more-than-unlikely scenario -- they must have branched off the human line at an even earlier date.
For Jungers and colleagues, this suggests "that the ancestor of H. floresiensis was not Homo erectus but instead some other, more primitive, hominin whose dispersal into southeast Asia is still undocumented," the researchers conclude.
Eleanor Weston and Adrian Lister of the Natural History Museum in London compared fossils of several species of ancient hippos found on the island of Madagascar with the mainland ancestors from which they had evolved.
They were surprised to find that insular dwarfing -- driven by the need to adapt to an island environment -- shank their brains far more than had previously been thought possible.
"Whatever the explanation for the tiny brain of H. floresiensis relative to its body size, our evidence suggests that insular dwarfing could have played a role in its evolution," they conclude.
The first fits with the wrist bone study.
The second is downright explosive.