The logical principle that the simplest explanation for the observed facts is preferred over more complex explanations. It is also known as Occam’s razor, after the English philosopher William of Occam (c. 1285–1349). The principle is often adopted in phylogenetics in construction of phylogenetic trees (phylograms) showing the ancestral relationships of different groups based on the minimum number of assumed evolutionary changes. When dealing with comparison of DNA or protein sequence data from different taxa, computer programs can construct all possible phylogenetic trees and identify the most parsimonious one that will fit the data—e.g. one that requires the fewest base changes in DNA. However, the principle can also be applied in constructing such trees based on other evidence, e.g. differences in morphological, developmental, or behavioural traits between the taxa.