A common objection to a plant-based dog diet is that dogs are sometimes classified as ‘carnivores’ (meat-eaters), like their ancestors wolves. It might be surprising to find out that the order Carnivore also includes some well-known omnivores such as raccoons and skunks, as well as the giant panda, which is a strict herbivore. From nutritional standpoint, this classification is misleading and inappropriate, and does not reflect evolutionary and physiological evidence about dogs. Modern dogs are now more appropriately classified as ‘omnivores’, that is, mammals that can receive their nutrients from both plant-based and meat-based diets. Although a dog’s ancestor is a meat-eating wolf, his digestive system changed over the past 10,000-36,000 years, due to adaption to domestication by humans.
From Wolf to Dog
Several archeological and genetic studies reveal that dogs emerged from wolves, like the Ancient Siberian Wolf.1,2 Ancestors of domesticated dogs started to live in close association with humans during the early agricultural revolution, and they scavenged from refuse and waste near human settlements. Perhaps as early as 36,000 years ago, dogs started adapting to human environments and nutrition.3
As a result of domestication, physiological systems of dogs slowly adapted to a varied diet, which consisted of both animal and plant-based products. Divergence of the dog and wolf genetic lineages over 10,000’s of years resulted the domestic dog as we know it today – very different from a wolf, physically and biologically.
In 2013, a group of researchers conducted a study which compared the dog genome (e.g. all the genes in the DNA) to the wolf genome. 4 They found that while dogs and wolves shared many genetic similarities, there were important differences between the two and they fell into two categories: 1) genes responsible for behavior traits and 2) genes that facilitate starch digestion.
In other words, this research showed that dogs are different from wolves in two main ways: personality (think temperaments of a wolf and a golden retriever) and an ability to digest carbohydrates. These differences make sense from an evolutionary standpoint – domestic dogs had to change their behavior in order to live alongside humans, and their digestive systems had to adapt to a human low-protein, carbohydrate-based diet.
The main biological consequence that resulted from genetic divergence of dog from wolf is the increased gene expression for pancreatic amylase (AMY2B) – a digestive enzyme which breaks down starch in the small intestine. 5 Ancient carnivores like the wolf, coyote, and golden jackal have only two copies of the AMY2B gene, limiting their ability to digest starch. Dogs, however, have more copies of the amylase gene (10-15 on average, the number varies among breeds), allowing them to effectively digest starchy foods.
Pancreatic amylase likely allowed dogs to survive on starch-rich diet during early domestication and allows modern dogs to consume a diet low in protein and high in grains. Other biological abilities of dogs include the ability to convert maltose to glucose and increased intestinal glucose uptake.6
These genetic and biological mechanisms shaped domestic dogs as we know them today, markedly different from the wolves they descended from. Dogs adapted to live with us, and it is natural for them to consume a diet that resembles ours, rich in grains and plants.
This post described an evolutionary argument for a plant-based dog diet. For information on nutritional perspective and to learn how well-balanced vegan dog nutrition works, please visit our Vegan Dogs 101 page.
Ancient wolf genome reveals an early divergence of domestic dog ancestors and admixture into high-latitude breeds. Curr. Biol. 2015, 25, 1515–1519.
A 33,000-year-old incipient dog from the Altai mountains of Siberia: Evidence of the earliest domestication disrupted by the last glacial maximum. PLoS ONE 2011, 6, e22821.
Plant-Based Diets for Dogs. Timely Topics in Nutrition. 253:11, 2018.
The genomics of selection in dogs and the parallel evolution between dogs and humans. Nature Communications volume 4, Article number: 1860 (2013)
Amylase activity is associated with AMY2Bcopy numbers in dog: implications for dog domestication, diet and diabetes. Anim Genet. 2014 Oct; 45(5): 716–722.
The genomic signature of dog domestication reveals adaptation to a starch-rich diet. Nature 2013, 495, 360–364