When did dogs become omnivores?
Dogs are members of the order Carnivora (i.e. they are carnivorans), but like many carnivorans, their dietary requirements are not carnivorous. Many carnivorans have developed distinct dietary habits, including omnivorous scavengers like the raccoon and panda bears that developed herbivorous dietary habits in the last 5,000-10,000 years. The evolutionary history and speciation of dogs away from their wolf ancestors were driven by adaptations to consume an omnivorous diet with large quantities of plant-based ingredients. Their domestication by humans guided their evolution from a mostly carnivorous diet to a starch-rich diet.
There is ongoing academic debate amongst evolutionary archeologists and geneticists as to whether dogs’ domestication happened when humans transitioned from primarily hunter-gatherer to agricultural societies ~10,000 years ago in the Middle East or potentially far earlier. Fossil records support the hypothesis that dogs consumed diets that were highly correlated with the diets of local humans (either directly fed or as scavenged trash), including almost entirely plant-based diets in Europe and the Middle East where meat was very expensive and humans primarily subsisted on grains and legumes. (Universitat de Barcelona, 2021).
The specific timing of domestication aside, dogs clearly show significant genetic adaptions to consume plants. A study conducted whole-genome sequencing of dogs and wolves to identify how DNA has diverged between the two species, and of the 36 regions of the genome that distinguish dogs from wolves, almost ⅓ of the genetic differences are related to dogs’ improved starch digestion and fat metabolism. (Nature, 2013).
In addition to fossil records and genome sequencing, recent digestibility studies have conclusively proven dogs’ adaptions to digest starches. A 2008 randomized study examined six starch sources common in dog food (cassava flour, brewer's rice, corn, sorghum, peas, and lentils) and found each to be over 98% digestible. (Carciofi et al, 2008) Plant-based foods have been included in commercial dog food since the inception of the industry, and the average companion dog is currently getting most of its energy from plant-based carbohydrates. The image of the wolf-like dog that must eat high quantities of meat and avoid grains has only become trendy in the last decade and is driven by human trends toward paleo and ancestral eating rather than nutritional science.
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