The domestication of the wolf larynx – testing the neural crest connection

The Neural Crest Domestication Syndrome (NCDS) hypothesis suggests that selection pressures for tameness during animal domestication result in a down-regulation of neural crest cell migration and proliferation, providing a mechanistic explanation to traits commonly observed across domesticates. We test the viability of this hypothesis via a derived prediction. According to the NCDS hypothesis, neural crest-derived structures should be reduced throughout the entire organism in domesticated variants compared to their wild ancestors. Here we test this prediction by comparing the larynx of the wolf and the domestic dog. Anatomical landmarking of the cricoid and thyroid cartilages confirmed absolutely and relatively shorter vocal folds and smaller larynges in mesocephalic dogs compared to wolves. Additional quantification of the laryngeal anatomy shows normal (mesocephalic) dogs to have a smaller cricoid diameter and shape-altered thyroid shields. As an exploratory extension, we further quantify the concrete anatomical changes to the laryngeal cartilages caused by brachycephaly, finding that a flattened thyroid shield and ventral cricoid ring fit the symptomatic descriptions of laryngeal collapse. Our comparison of larynges of wolves and dogs are in line with the NCDS-derived prediction and support the validity of the Neural Crest Domestication Syndrome Hypothesis. Methods Data was collected via geometric morphometric analysis of 3D models generated from CT scans of larynges