THREE wrist bones from one of the tiny "hobbits" of Indonesia provide the evidence that confirms they are a new species of humans, scientists report.

Since the discovery of the prehistoric humans on the island of Flores was announced three years ago, debate has raged over whether the fossils are a new species, called Homo floresiensis .

Much of the contention has been over the skull of a one-metre tall female with a grapefruit-sized brain known as LB1. Detractors argue the skull came from a modern human with microcephaly, a brain-shrinking disorder.

But a team of scientists using laser imaging to study LB1's wrist bones said the anatomy was very primitive, much more like apes and older human ancestors, than modern humans.

Wrist bones in modern humans are shaped so force is better distributed across the wrist, from the base of the thumb towards the little finger. This is useful for grabbing objects.