Pleiotropy is a pervasive phenomenon in evolution. Its relevance and existence were recognized early in medical syndromes, but the term "pleiotropy" was first coined by Ludwig Plate in 1910 (Stearns, 2010). Pleiotropy is an important concept with many different facets and definitions, but generally describes "the phenomenon of a single gene affecting multiple traits" (Paaby & Rockman, 2013). Here, we investigated the emergence of unselected by-products coupled to an originally selected for trait, including across developmental stages, as a possible example of pleiotropy, but we make no claims about genetics (Paaby & Rockman, 2013). Coherent development throughout developmental stages is essential for functionality in morphological structures (Cheverud, 1996), and pleiotropic traits can thus be representative of adaptive developmental processes that form and shape structures in organisms (Klingenberg, 2008). A potential example of a pleiotropic effect can be found in dogs and other domesticated mammals. Human selection for tameness in these animals has been suggested to lead to downregulation of neural crest cell development and migration (Wilkins, Wrangham,

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