Apr 18, 2007
PARIS (AFP) - A tantalising piece of evidence has been added to the puzzle over so-called "hobbit" hominids found in a cave in a remote Indonesian island, whose discovery has ignited one of the fiercest rows in anthropology.
Explorers of the human odyssey have been squabbling bitterly since the fossilised skeletons of tiny hominids, dubbed after the diminutive hobbits in J.R.R. Tolkien's tale, were found on the island of Flores in 2003.
Measuring just a metre (3.25 feet) tall and with a skull the size of a grapefruit, the diminutive folk lived around 20,000 and 80,000 years ago and appear to have been skillful toolmakers, hunters and butchers.
They have been honoured with the monicker Homo floresiensis by their discoverers, who contend the cave-dwellers were a separate species of human that descended from Homo erectus, which is also presumed to be the ancestor of modern man.
That claim has huge implications and has been widely contested.
If true, it would mean that H. sapiens, who has been around for around 150,000-200,000 years, would have shared the planet with rival humans far more recently than thought.
And it implies that H. sapiens and H. floresiensis lived side by side on Flores for a while -- and, who knows, may even have interbred, which could have left "hobbit" genes in our DNA heritage.
In a study that appears on Wednesday in the British journal Biology Letters, evolutionary zoologists at Imperial College London believe the hobbits may well have achieved their tininess naturally, through evolutionary pressure.
The principle under scrutiny here is called the "island rule."
It stipulates that because food on a small island is limited, smaller species do well and get bigger over time, sometimes becoming relatively gargantuan.
But larger species, facing fierce competition for a small amount of food, become smaller, because those members that eat less have an advantage.
Lindell Bromham and Marcel Cardillo trawled through published journals and online databases to see how primates performed when subjected to the "island rule."
True enough, small primate species (ones weighing less than five kilos, 11 pounds) all pumped up compared to their mainland relatives -- but all the larger primates became smaller, in a range of between 52 and 80 percent.
That fits in well with H. floresiensis, who was around 55 percent of the mass of a modern Indonesian and probably 52 percent of an H. erectus.
So the evidence backs the idea that the hobbits were an insular dwarf race -- humans who became smaller, possibly after the island separated from the mainland and left them marooned with diminished food resources.
The authors refuse, though, to wade into the debate as to whether the hobbits were H. erectus or H. sapiens.
Also unclear is why the hominids had a relatively undersized brain compared to their diminutive body. A modern human child of the same size has a much larger brain, as do pygmies.
A conflicting explanation for the small brains has been offered by primatologists led by Robert Martin of the Field Museum in Chicago.
He contends that the Flores hominids were not a separate species but quite simply a tribe of H. sapiens who suffered from a pathological condition called microcephaly, which results in a small brain and body.
Martin also disputes the idea that these pint-sized creatures could have wielded the sophisticated stone tools, found in the Flores cave, which were used to butcher animals.
The hobbits tucked into a now-extinct miniature elephant, Stegadon, that also dwarfed-down under the "island rule".