Testing the Self-Domestication Hypothesis: How Convergent are Dogs' Cooperative Communicative Abilities with those of Humans?

Homo sapiens’ capacity for cooperative communication enables us adapt to new environments more rapidly than any other species via the process of cumulative cultural evolution, but the evolutionary processes which led to this capacity remain an open question (Boyd & Richerson, 1995; Henrich & McElreath, 2003; Hill et al., 2009; Mesoudi & Thornton, 2018; Tomasello, 1999). One proposed explanation for this capacity is the human self-domestication hypothesis (SDH), which posits that cooperative communication was altered via shifts in development as a by-product of self-selecting against aggression and for prosociality (Hare, 2017; Hare et al., 2012). Dogs have been hypothesized to have undergone the same process during their domestication, resulting in human-like cooperative communicative abilities (Hare, 2017). If so, this convergence could make dogs a critical model for human self-domestication. The present dissertation evaluates this hypothesis by testing three resulting predictions: 1) that dogs’ understanding of communicative intentions is actually “human-like” (i.e. spontaneous and flexible), which we tested through a series of gesture reading tasks with adult dogs; 2) that these qualities are a result of domestication, and therefore expressed more strongly and at an earlier age in dogs compared to wolves, which we tested by running dog and wolf puppies through a cross-sectional battery of cognitive and temperament tasks; and 3) that dogs show early emerging and expanded windows of social development relative to other non-social cognitive abilities, indicating a similar developmental pattern as is observed in humans, which we tested by running puppies through a longitudinal battery containing nine cognitive tasks during the period of rapid brain development. Strong support was found for predictions 1 and 2, and some support was found for prediction 3, with more work being needed to draw stronger conclusions. We conclude that dogs’ cooperative communicative abilities are convergent with those of humans at the levels of behavior, cognition, and potentially development as well.