Everyone knows that the purpose of fingerprints is to increase friction and therefore improve our grip. New research calls this common belief into question – sort of.

The media, and it seems the researchers themselves (if they are being presented accurately) are presenting this as scientific evidence debunking a myth – but the real story is more complex.

Dr. Roland Ennos did a number of experiments looking at the friction between a finger pad and a plate of glass. He found that the friction did not increase by much when the force between the finger and glass increased – less than predicted. However, the friction did increase in proportion to the surface area of the finger pad that was in contact with the glass.

This means that finger pad skin behaves more like rubber – where friction is mainly a function of surface area, not the force of contact.

What this further means is that the ridges of fingerprints actually decrease the surface area of contact, and therefore decrease friction – rather than increase it, as was expected. That’s interesting, and certainly counter-intuitive.

However, that is not the whole story, and it does not mean that fingerprints are not useful for grip. Ennos only studied smooth surfaces, and it is possible that fingerprints may increase grip with rough surfaces. Other hypotheses are that fingerprints increase grip when wet – the channels allow for water to be carried away from the finger pads. Or that they increase sensitivity.

What struck me, and what the article did not mention, is that glass is a very artificial material. It is unlikely that our ancestors would have encountered such smooth material often in their day-to-day lives. Therefore there would not have been much selective pressure to develop a good grip on glass or similarly smooth material. Tree branches, rocks, fur, bones, and other materials that might find their way into the grasp of a hominid or ape are much rougher than glass.

Clearly follow up research is needed. How do fingerprints behave when applied to other materials, and how does wetness affect their utility?

What interested me most about this story is how the media channels science news stories into a few themes with which they feel comfortable. Debunking a commonly held myth is one of those themes. While this story hold a kernel of that theme – it is more accurate to say, in my opinion, not that the grip hypothesis is wrong but that the story is more complex.

That is a much more useful theme for science reporting – because the story is almost always more complex – more complex than the typical publish understanding, and even of our previous scientific understanding.

Likewise, it is more meaningful in many cases to portray our prior models and theories not as “wrong” but as incomplete. Sometimes they are wrong, but that needs to be distinguished from ideas that are oversimplified and therefore incomplete, but not wrong.

A recent relevant example of this is the New Scientist article on Darwin’s tree of life. The theme of the reporting, boldly declared in the headline, was that the tree of life is wrong – a debunked idea. This was greatly misleading, however, and lead to a misunderstanding and a great deal of mischief at the hands of the boobs over at the Discovery Institute.

The evolutionary tree of life is the basic concept that all life on earth is related through common ancestry and branching descent. This pattern includes only “vertical” genetic transfer – from parent to child. What the New Scientist article was discussing was emerging information about the extent of horizontal gene transfer – such as the swapping of genes between strains of bacteria. It turns out there is much more horizontal transfer, even among vertebrates, than was previously known. Viruses, for example, may act as vectors for carrying genes from one species to another.

This information, however, does not invalidate the tree of life. Horizontal transfer may be greater than previously known, but it is still a minor factor compared to the branching descent that dominates the tree of life, especially for multi-celled organisms. The tree of life is not wrong – it is still mostly correct.

It is as correct as saying that the Earth is a sphere. The spherical Earth theory is very useful, correct for most purposes, and is sufficient for working with other theories, such as gravity and plate tectonics. But it is not completely accurate – the Earth is really an oblate spheroid and slightly larger in the Southern hemisphere.

Similarly, the tree of life is true enough, and supports the underlying theory of evolution, and is sufficient for most purposes. But it needs to be tweaked with an understanding of the contribution of horizontal transfer. Saying the tree of life is “wrong” is to profoundly misunderstand the science, which the ID goons happily did. And New Scientist was lambasted for this botching of science reporting, as they should have been.

The difference between wrong and incomplete is very important to the proper understanding of the history and progress of science. I wish the science reporting media would getter a better “grip” on this idea (hey, I had to bring it home somehow). In fact, they need to expand and improve their repertoire of science writing themes – so that they more often tell the real story rather than just the story they want to tell.