Freshman Undergraduate Biology Students’ Difficulties with the Concept of Common Ancestry

摘要

All life on earth descended from a single common ancestor that existed several billion years ago; thus, any pair of organisms will have had a common ancestor at some point in their history. This concept is fundamental to an understanding of evolution and phylogeny. Developing an understanding of this concept is an important goal of evolution education and a part of most high school and college biology curricula. This study examines freshman undergraduate biology majors’ understanding and application of the concept of common ancestry. We used a survey that asked students to provide a brief definition of common ancestry and to rate their confidence that different pairs of organisms shared a common ancestor. Our results show that, although many students in our sample could give a satisfactory definition of common ancestry, the overwhelming majority failed to apply their definitions correctly when assessing the likelihood that the pairs of organisms shared common ancestors. Instead, we found that these students do not treat common ancestry as a binary (yeso) trait, but instead see it as a continuum from less probable to more probable. These students are more likely to think that closely related organisms have a common ancestor than those that are more distantly related and that humans are less likely to be connected to common ancestors than nonhuman organisms. This pattern is highly consistent from student to student and has important implications for teaching evolution.