Citation: Sandvik, H. (2008) Tree thinking cannot be taken for granted: challenges for teaching phylogenetics. Theory in Biosciences, 127, 45–51.
Key words: Biological education, cladogram, essentialism, evolutionary tree, group thinking, stem group.
Abstract: Tree thinking is an integral part of modern evolutionary biology, and a necessary precondition for phylogenetics and comparative analyses. Tree thinking has during the 19th century largely replaced group thinking, developmental thinking and anthropocentricism in biology. Unfortunately, however, this does not imply that tree thinking can be taken for granted. The findings reported here indicate that tree thinking is very much an acquired ability which needs extensive training. I tested a sample of undergraduate and graduate students of biology by means of questionnaires. Not a single student was able to correctly interpret a simple tree drawing. Several other findings demonstrate that tree thinking is virtually absent in students unless they are explicitly taught how to read evolutionary trees. Possible causes and implications of this mental bias are discussed. It seems that biological textbooks can be an important source of confusion for students. While group and developmental thinking have disappeared from most textual representations of evolution, they have survived in the evolutionary tree drawings of many textbooks. It is quite common for students to encounter anthropocentric trees and even trees containing stem groups and paraphyla. While these biases originate from the unconscious philosophical assumptions made by authors, the findings suggest that presenting unbiased evolutionary trees in biological publications is not merely a philosophical virtue but has also clear practical implications.
Full text: © 2008 Hanno Sandvik. If you accept (i) the conditions specified in the Springer Open Choice Licence, and (ii) that printouts have to be made on recycled paper, you may download the article here (pdf, 0.2 MB).
Note (added after proof): A paper by Gregory (2008) on "understanding evolutionary trees" is very relevant to my article, but appeared too late to be included in my reference list.