Academic journal article Merrill-Palmer Quarterly

Can Children Read Evolutionary Trees?

Academic journal article Merrill-Palmer Quarterly

Can Children Read Evolutionary Trees?

Article excerpt

Representations of the "tree of life" such as cladograms show the history of lineages and their relationships. They are increasingly found in formal and informal learning settings. Unfortunately, there is evidence that these representations can be challenging to interpret correctly. This study explored the question of whether children aged 7-11 can read these trees and, if so, what factors influence their understanding. A total of 28 children were shown dadograms with both different content (species and features shown) and form (how branches rotated). Questions required these children to reason about different aspects of cladogram interpretation and to search varying depths of the tree. Overall, children did remarkably well: 56% of their answers were completely correct after only 15 minutes of instruction. The youngest quartile of children performed worse than other ages, but there were no further age differences. Children's performance was influenced by the content and the depth of tree searched but not by the rotation of the branches. Like adults, they found reasoning about the relatedness of species particularly difficult. Children's explanations revealed varied insights: from correct semantic interpretation to syntactic interpretation to a variety of misunderstandings. Demonstration of this basic competency provides a foundation from which to design a more extended curriculum for children that uses cladograms to support evolutionary understanding.

Representations of the tree of life (e.g., cladograms as in Figure 1 and especially Figure 2) show the evolutionary history of life and provide an insight into the history of lineages and how they change over time. Biologists can use such trees to test hypotheses about evolution, classify organisms in new ways, and learn about the characteristics of extinct species. Cladograms and related forms of phylogenetic trees have played roles in such diverse areas as the discovery of new biological compounds, restoring damaged ecosystems, and understanding the functional role of genes (Cracraft & Donoghue, 2004).

Tree diagrams are increasingly found not only in specialist journals but in school and college textbooks, popular books (e.g., Dawkins, 2004), and museums. For example, when Catley and Novick (2008) reviewed 31 textbooks commonly used in high schools, universities, and colleges, they found that 72% of the diagrams of evolution were cladograms. When Macdonald and Wiley (2012) surveyed the use of cladograms in informal science institutions, including natural history museums, zoos, and aquariums, they found that cladograms were used frequently (25% of thensample), but that the use of tree diagrams, which have superficial resemblance to cladograms, is more frequent (38%) - a concern because research suggests these can be difficult to interpret correctly.

Unfortunately, there is growing evidence that college and high-school students are prone to misread cladograms and draw erroneous conclusions from them (Gregory, 2008; Halverson, Pires, & Abell, 2011; Meir, Perry, Herron, & Kingsolver, 2007) and that even experts in evolution can be misled at times (e.g., Krell & Cranston, 2004). Given these problems, it does seem optimistic to expect children to be able to interpret cladograms successfully. Yet, if they can interpret and construct simple cladograms, this would help prepare them for high-school and college education. In a now well-known analogy, O'Hara (1997) claims that just as geography students are taught to read maps, so biology students should learn how to interpret evolutionary trees. Map interpretation begins in the early years of formal education (e.g., Uttal & O'Doherty, 2008), can cladogram interpretation do likewise? Accordingly, the research reported in this article explored whether 7- to 11 -year-old children can draw appropriate inferences from simple cladograms.

Reading Cladograms

We begin by briefly explaining how to interpret a cladogram. …

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