Making sweet music

BIOLOGICAL evolution happens by random mutation and selection. Technological evolution involves selection, too. Products preferred by customers are the ones that reproduce. But since technology is the product of conscious design, the mutation part of the process might reasonably be assumed to be deliberate rather than random.

A study just published in the Proceedings of the Royal Society suggests, however, that this is not always the case. Nicholas Makris and his colleagues at the Massachusetts Institute of Technology, in collaboration with Roman Barnas, a violin maker at the North Bennet Street School, in Boston, have been looking at the evolution of that instrument. One aspect of the process intrigued them in particular—the changing shape, over the years, of the holes in a violin’s body that allow the sound to emerge.

The violin’s oldest European ancestors date from the tenth century. They were called “fitheles”, a word derived from vitula, the Latin for heifer, the source of the gut for the strings. (The Latin word also eventually gave rise to “violin”; “fitheles”, meanwhile, became “fiddle” in a process of linguistic speciation also akin to the biological sort.) The instrument arrived at its modern form between the 16th and the 18th centuries, in the workshops of Cremona, a city in northern Italy that produced the Amati, Guarneri and Stradivari dynasties of luthiers.

Dr Makris and his team noticed that, in the transition from tenth-century fithele to 18th-century violin, the holes on top of the sound box evolved from simple circles to the complex, elongated f-shapes familiar in today’s instruments. They wondered why.

The answer, arrived at after several pages of advanced mathematics, and confirmed by experiment, is that holes’ sound-amplification properties depend not on their areas but on the lengths of their peripheries. They showed how the shape of the hole varied over the centuries, and how that affected its power output. The final Cremonese design had twice the sonic power of the circular holes of the fithele.

Except that Dr Makris doubts “design” is precisely the right word for what happened. Design implies intent. But his analysis of 470 Cremonese instruments made between 1560 and 1750 suggests, as the chart shows, that change was gradual—and consistent, in Dr Makris’s view, with random variations in craftsmen’s techniques producing instruments of different power. The market, presumably, favoured those journeymen within a workshop who made more powerful instruments. When they became masters in their turn, they then passed their ways of doing things on to their own apprentices. Only at the very end of the period might a deliberate change have been made, as the holes get suddenly longer.

Intriguingly, intentional attempts in the 19th century to fiddle further with the f-holes’ designs actually served to make things worse, and did not endure. As is also the case with living organisms, mutation and selection seem to have arrived at an optimal result.