Bronze-Age Dogs and Humans Both Ate High-Carb Diets

By Claudia Kawczynska, June 2019
Chronicle / Alamy Stock Photo

Chronicle / Alamy Stock Photo

Have you ever wondered what the life of ancient dogs was like—what they ate, what they did, who took care of them? A recent (and fascinating) study of Bronze Age proto-farmers and their dogs offers some answers, and another way of understanding canine dietary requirements as well. Spoiler alert: “paleo” doesn’t seem to have been the universal standard.

By the Bronze Age (roughly 4,000 to 5,000 years ago), dogs were firmly in the human camp, having made the big evolutionary leap from wolf to domesticated canine thousands of years earlier. This was also a time during which many groups of humans were shifting from being nomadic hunters and gatherers to a more settled agrarian existence. The dogs living with agro-pastoral families most likely had jobs involving livestock herding, guarding and drayage, or hauling.

To get a clearer idea of the role dogs played in Bronze Age village life, a team of Spanish researchers studied the diets of both humans and canids via analyses of ancient bones. Looking at dogs as they lived with us during the birth of agriculture opens up a whole new line of inquiry: how did they become omnivores?

Back to the science. Earlier this year, the team of researchers led by Aurora Grandal-d’Anglad, Silvia Albizuri and Arianda Nieto published the results of their work in Archaeological and Anthropological Sciences. Titled “Dogs and foxes in Early-Middle Bronze Age funerary structures in the northeast of the Iberian Peninsula: human control of canid diet at the sites of Can Roqueta (Barcelona) and Minferri (Lleida),” it detailed the analyses of the bones of 37 canids (33 dogs, 4 foxes), 19 domestic ungulates and 64 humans recovered from grave sites in northeastern Spain. Many of the dogs (as well as other domestic species, including the four foxes) were co-buried with humans.

The region’s main crops were barley*, wheat and legumes. Milk products were also likely part of the diet; perforated vessels thought to be strainers were found at these sites, evidence of rennet processing and filtering in the preparation of yogurt and cheese.

The researchers measured stable carbon and nitrogen isotopes found in bone collagen, using the carbon content of cattle bones to determine the baseline for a herbaceous diet. The carbon reading indicates vegetable matter, while the nitrogen signals protein, including that found in legumes. The isotopic signatures that showed up in these analyses suggest that, while dogs at the two sites didn’t eat the same food in the same proportion as humans, they shared an overall similarity, especially with females and children, who consumed less protein than males: meals of gruel/porridge, along with varying degrees of animal protein and protein from yogurt/whey made from ungulate milk. The co-burial patterns of females and children with canids also suggest a greater dedication by this group to the nurturance and care of dogs, including preparing meals for them.

Early Christian, Roman sarcophagi. Shepherd with dog.  Unknown. 3rd–4th Century AD. Vatican Museums.  Photo credit: Lanmas / Alamy Stock Photo

The dogs found at the two sites were of medium size, respectively 17.5 and 19 inches on average at the withers (the ridge between a dog’s shoulder blades). Their weight varied as well: at one site, 31 to 43 pounds and at the other, 18.5 to 32 pounds. The lumbar vertebrae of the larger dogs displayed bent spinous processes (the bony projection on the back of each vertebrae), which was interpreted as evidence that they had regularly borne vertical loads on their backs. Think travois or carts, similar to the practice in not only ancient settlements but also among Paleo-Indian dogs in Alabama and Illinois.

The researchers concluded that the dogs were purposely fed a diet high in plant material and some protein, probably from bones and leftover meat, muscles and tendons, or even from dairy products. However, they could not rule out that the protein might also have come from the dogs’ habit of opportunistic feeding.

Based on evidence presented in a 2016 study by Ollivier, et al. (“Amy2B copy number variation reveals starch diet adaptations in ancient European dogs”), the researchers also note that “cereals are not a foreign food for dogs, because—parallel to the development of agriculture—dogs, like humans, were developing ways of improving digestion of starch through the multiplication of copies of the amylase gene.” (The body uses amylase, an enzyme produced primarily by the pancreas and salivary glands, to help digest carbohydrates.) As mentioned in the 2016 study, this genetic adaptation has been found as far back as 7,000 years before the present.

With this gene-level change, dogs—who, as we know, evolved from gray wolves perhaps 50,000 years ago—developed the ability to derive nutritional value from a high-carb diet, a trait they had in common with the humans who shared their bowls of mush with them. As they did in so many other ways, dogs synced up with us as we traveled the road from nomadic hunter-gatherers to settled grower-harvesters.