Paedomorphic Facial Expressions Give Dogs a Selective Advantage

Abstract

How wolves were first domesticated is unknown. One hypothesis suggests that wolves underwent a process of self-domestication by tolerating human presence and taking advantage of scavenging possibilities. The puppy-like physical and behavioural traits seen in dogs are thought to have evolved later, as a byproduct of selection against aggression. Using speed of selection from rehoming shelters as a proxy for artificial selection, we tested whether paedomorphic features give dogs a selective advantage in their current environment. Dogs who exhibited facial expressions that enhance their neonatal appearance were preferentially selected by humans. Thus, early domestication of wolves may have occurred not only as wolf populations became tamer, but also as they exploited human preferences for paedomorphic characteristics. These findings, therefore, add to our understanding of early dog domestication as a complex co-evolutionary process.

Development and application of CatFACS: Are human cat adopters influenced by cat facial expressions?

“…proportionally shorter snout: Morey, 1994) and it is thought that the inner brow raiser acts to enhance the already very paedomorphic features of the dog. Thus, Waller et al (2013) suggested that this particular facial expression explores, in some way, the sensory preferences of humans and consequently, drives the domestication process in this species. In cats, the neotenisation processes seem to be restricted to the vocalisations (Nicastro, 2004;Yeon et al, 2011) and do not seem to be present in facial expressions.…”

“…Waller et al (2013) used rehoming speed from dog shelters to assess whether specific facial expressions gave dogs a selective advantage in attracting human investment (adoption). Dogs displaying higher frequencies of brow raises were preferred by future adopters.…”

“…Vick et al, 2007;Waller et al, 2013). First, we examined the existing literature on the facial musculature of the domestic cat and performed a subsequent comparison with humans' facial musculature (Ekman et al, 2002;Diogo et al, 2009Diogo et al, , 2012 to identify possible muscular homologies.…”

“…Original dissections of the facial muscles have been carried out in some cases (e.g. Vick et al, 2007;Waller et al, 2013), but due to the extensive literature available on the facial musculature of the domestic cat (Mivart, 1881;Reighard and Jennings, 1901;Davidson, 1927;Crouch, 1969;Done et al, 1996;Tomo et al, 2002), this was deemed unnecessary. Second, the form and location of muscles were matched to observed facial movements by analysing frame-by-frame spontaneous facial behaviour from video footage.…”

“…The cat shelter adoption process can therefore be interesting to scientists not only from a welfare perspective, but also as a proxy for human preference for certain cats over evolutionary time. Waller et al (2013) used dogs rehoming rates to assess whether certain behaviours gave dogs a selective advantage in a shelter environment. The research team concluded that dogs displaying higher frequencies of a very subtle brow raise were preferred by future adopters, likely due to a paedomorphic effect.…”