Through civilization, humans have sought out animals for companionship and help with hunting and guarding. From this, some societies have bred for certain traits within their animals, such as big bodies or fluffy fur. This selective breeding has been helpful, but it has also made some breeds have health conditions from birth, according to smithsonianmag.com.

Munchkin Cats
These cats are known primarily for their short legs. They started out as a genetic mutation in a litter of kittens. From there, they were bred for their short legs, as it was appealing to some people because of their uniqueness. This breed is prone to spinal issues because of their legs and can have issues jumping normally. They also have increased risks of problems with their joints, which can cause them to have chronic pain, according to mylovelyfeline.com.

Teacup Dogs
While this is not a specific breed, it can include Shih Tzus, Chihuahuas or Pomeranians. They are characterized by their tiny size, with most weighing less than 10 pounds. These dogs are usually bred unethically, with breeders looking to make them as small as possible. They typically have a lot of health issues, including hypoglycemia, which is low blood sugar levels, hydrocephalus, which is water that sits on their brains and causes extra pressure in their skull, and dental issues because of their tiny mouths, according to petmd.com.

Persian Cats
These kitties are flat-faced and long-coated. They date back very far, into the 1600s, and were owned by royal families. They were bred for their “beautiful coats” at first and were not actually known by their flat faces until the 1950s. A litter of Persians were born with flat faces, and they were adored by breeders. These cats usually have a lot of issues, including hydrocephalus, brachycephalic airway syndrome, which is trouble breathing because of narrow nostrils, and coat and skin problems, like infections, according to petmd.com.

Pugs
Like the favorite Persian cat, they are flat-faced and small in size. They were bred for wealthy people as they were seen as royalty by some because of their flat faces. They have some similar issues to other flat-faced breeds, such as brachycephalic airway syndrome. Pugs also commonly suffer from eye ulcers and infections because of their protruding eyes, according to purina.co.uk.

Now that these issues have come to light to breeders, some are trying to breed bad traits out of their animals, rather than furthering the issue. Different breeders across the world are pushing for laws that ban improper breeding habits, like breeding flat-faced animals or short legs. In New Hampshire, a bill was introduced that would outlaw the breeding of dogs or other animals with brachycephaly. Similar strides are being taken in European countries like Germany, where they are proposing bans on animals with skeletal issues that would cause pain, such as short legs, according to news.northeastern.edu.