A machine that runs an artificial finger across different types of surface is being used to investigate the evolutionary origins of the pattern of ridges on the ends of our digits
It seems intuitive that fingerprints should have something to do with grip, but showing this has not been easy.
Many experiments that have run human skin across various surfaces have found few if any friction benefits from the little lumps and bumps.
But new tests using an artificial finger may provide some fresh insight.
A Dartmouth College team took its mechanical digit into the field and ran it over natural materials like tree bark and found a big friction increase.
The observation is interesting because it could say something quite deep about the evolution of primates.
Only our order of animals, with a few exceptions, has these ridges, or dermatoglyphs, on the ends of fingers and toes.
The research would suggest therefore that the prints gave our ancestors a unique advantage as they clambered through ancient forests.
It is striking, says Dartmouth's Nathaniel Dominy, that the advantage shows up particularly well when natural materials are used in the experiments. Previous laboratory tests have tended to use many fingers moving across a smooth standard surface, such as a glass.
In the Dartmouth approach, it is the finger that is the control and the substrates that are varied.