Tiny skeletons found in the caves of the Pacific islands of Palau undercut the theory that similar remains found in Indonesia might be a unique new species of humans, researchers report.

The Palau skeletons, which date to between 900 and 2800 years old, appear to have belonged to so-called insular dwarfs, humans who grew smaller as a result of living on an island, the researchers say.

They say their findings, published in the Public Library of Science journal PLoS ONE, show it is possible the same thing happened on the Indonesian island of Flores.

This is where small skeletons dating 15,000 to 18,000 years old have intrigued scientists since they were discovered in 2004.

Professor Lee Berger of the University of the Witwatersrand in Johannesburg, South Africa, and colleagues say they cannot explain the Flores skeletons.

But they say they found some similar remains in Palau, one of the islands of Micronesia.