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Q42 - Adaptations, Spandrels, and Developmental Constraints

Theoretical 2 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Evolutionary Developmental Biology (Evo-Devo)

Basilica of St Mark in Venice is an architectural marvel built in the 11th century CE. When examining the architecture, it is hard to avoid the spandrels in the corners of the ceiling, like the one in the figure (the triangular shape delineated by the dotted lines). Gould & Lewontin (1979) argue that these spandrels are the result of simple geometric constraints one encounters when trying to hold a dome with column and arches. If we were to use the tools of evolutionary biology we would at first consider the spandrels as “adaptations” for the purpose of having the decorations, but in fact they are non-adaptive features, and we cannot count them as adaptations.

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. If the feather characteristic of birds first evolved in dinosaurs for the purpose of thermal regulation, that feather is similar to spandrels.
B. When investigating the evolution of small regulatory RNAs (where the phenotype is closely tied to the genotype), biologists should not presume adaptation to avoid mistaking "spandrels" for true adaptations.
C. Biological "spandrels" are more common in species with historically high population size.
D. The evolution of big brain in humans would be a biological spandrel if its evolutionary trajectory is constrained by developmental process in primates.
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Question reproduced from IBO 2018, Theoretical Paper 2, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)