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

Abstract

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 (yes/no) 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.

Exploring the influence of plant and animal item contexts on student response patterns to natural selection multiple choice items

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Teaching undergraduate students to draw phylogenetic trees: performance measures and partial successes

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Accepting, understanding, teaching, and learning (human) evolution: Obstacles and opportunities

“…Catley et al () demonstrated that students’ understanding of tree‐thinking and macroevolutionary concepts can be substantially increased by focused instruction, but noted that they still struggled with the concept of most recent common ancestry (MRCA), which they argue is not made explicit in biology textbooks but should be. Common ancestry was also found to be a difficult concept in a study for freshman undergraduate biology majors, who consistently saw common ancestry as a continuum from less to more probable rather than a binary yes/no trait, viewed taxonomic distance as the most significant factor in determining the likelihood of common ancestry, and thought that humans are less likely to be connected to common ancestors than nonhumans are (White and Yamamoto, ). A study that compared two semesters of an introductory biology class in which tree‐thinking was taught as an organizing framework for the course with one in which those concepts were taught as stand‐alone topics found significant increases in students’ ability to read trees in both semesters, but a significant increase in students’ acceptance of evolution only in the former semester—and that post‐test evolution acceptance was correlated with gains in tree‐thinking abilities (Gibson and Hoefnagels, ).…”