Here's what the animals we eat looked like before we started breeding them

We've bred many animals to unnatural proportions, and turkeys may be the most drastic example. Turkeys of the 1930s were, on average, 13.2 pounds, but by 2014, an average turkey weighed in at a whopping 29.8 pounds — almost twice as large, according to Mother Jones. Just check out the turkey JFK pardoned in 1963 (left), compared to the one Obama pardoned in 2013 (right).

The breeding of beef cattle can be traced back to the efforts of British agriculturalist Robert Bakewell in the 18th century, who bred them to be larger and meatier than ancestors like the Wild Cattle of Chillingham (left). The most extreme example today is the Belgian Blue (right), a cow bred to have twice the normal amount of muscle.

Domestic sheep are thought to have descended from the wild mouflon of Europe and Asia (left). Robert Bakewell also played a large role in breeding sheep to be big but delicately-boned, with high-quality fleece and fatty forequarters (right).

Modern pigs (right) were probably domesticated from the wild boar (left) 9,000 years ago in Asia, but weren't introduced to Europe until the 18th or 19th century. Farmed pigs lack the tusks and coarse fur of their wild brethren, and are prized for their tender, fatty meat.

Domestic chickens (right) are descendants of the red junglefowl (left), which are technically the same species. They may have originally been bred for cockfighting, but today they are raised primarily for their meat and eggs. Sadly, most chickens today are raised in factory farms, under what many consider inhumane conditions.

While we often think of breeding as applying only to land animals, let's not forget fish farming. Atlantic salmon have been bred to be larger as well as feed faster than their counterparts in the wild. And now, we've even developed a genetically modified salmon (pictured), which contains a gene that allows it to grow faster than conventional salmon.