Violist Dan Chitwood, a biologist who ordinarily studies leaves, employed the skills and analysis methods normally used to quantify leaf shape over time to study how string instruments have evolved. He looked at an auction house database of 9,000-plus string instruments (violin, viola, cello, bass) built by prominent luthiers over a 400-year time frame to compare instrument outlines using linear discriminant analysis. While violas and violins were harder to distinguish based on shape, cellos and double basses were more distinct. Chitwood discovered that violins fell into four families—Maggini, Amati, Stainer, and Stradivari (whose violins were slightly more bass-like in shape). Other violins became more like these four types over time, especially more like the Strads. Chitwood also discovered that the approximately 1,000 instruments built by Antonio Stradivari from roughly 1666-1737 evolved in terms of shape, despite his use of molds. Also, luthier Jean-Baptiste Vuillaume, who built around 3,000 instruments from 1823-1875, purposefully copied Stradivari’s designs because they were preferred by customers.