Pronunciation & Etymology: It is a phrase made from two common English words.

Branch length refers to the number of changes that occur in a clade or a whole phylogram (cladogram whose branch lengths are relative to the number of changes). Following Occam’s principle, the shortest tree length is the most acceptable cladogram.

The numbers associated with the branches in the following cladogram indicate branch lengths relative to the particular character set. The difference between a man and a monkey is 1 (0.5 + 0.5). However, the difference between a monkey and a moth is: 36.4 (18.2+4.00+6.30+1.65+5.75+0.5). These values were generated from a particular character set, so the absolute value of the outcome would be different given the characters examined. However, the general outcome would be the same.

© David Thomas, “Charles Darwin et. al. on Hierarchies and Phylogenies,” October 2002A,
http://www.nmsr.org/darwin.htm

By Jack R. Holt. Last revised: 01/02/2009