It’s fascinating to think that crossbreds are essentially the legos of the natural world; only instead of plastic bricks and toy blocks, different animals mixed and matched until something far more interesting, eye-catching, and fun to play took shape. But much like overpriced lego blocks, crossbreeding generally does not come without a cost.

Artificial selection, otherwise referred to as selective breeding, is a rather convenient way of phrasing our ability as human beings to proactively shape the evolution of other animal life forms to serve our preferences, curiosity, and often times entertainment.

What follows is a list of popular crossbreds that, despite their domestic prominence, suffer from mutations that have negatively affected their evolution.

1. Large Tail Han Sheep

Also referred to as Fat-Tailed Sheep, the Large Tail Han Sheep is a domestic Mongolian sheep that is best known for its excessively large tails and hindquarters. It is widely believed that the Large Tail Han Sheep was originally developed in the agricultural regions of Henan, Hebei, Shandong, Anhui, and Jiangsu Provinces. Today, this sheep is most commonly raised in the Northern parts of Africa, the Middle East, and parts of Central Asia.

The distinctive physical profile of the-the Large Tail Han Sheep is specifically designed by professional crossbreeders to keep most of the subcutaneous fat of the animal localized in their tails. The purpose of localizing the sheep’s fat store is to make it rather convenient for people to harvest the fat as cooking oil after the sheep is dead. Fat stores of the sheep have been extensively used in most Arab and Persian cuisines during the medieval times.

Despite being tough and durable, the unique physical features of the Large Tail Sheep has made it suitable only for the plains. With an oversized tail weighing as heavy as 25kgs, the Large Tail Han Sheep has a difficult time moving around during grazing.

2. Dong Tao Chicken

The Dong Tao Chicken, fondly called as Dragon Chicken, is a domesticated fowl crossbreed that is most recognizable for its disproportionately oversized feet. This crossbreed got its name from the town where it is believed to have originated from—the small provincial village of Dong Tao in Khoai Chau District that sits 30kms from Hanoi.

Due to its limited numbers, the Dong Tao chicken is one of the few a rare domesticated chicken breeds in the world. Prized for its delicious meat, the Dong Tao chicken was once only bred exclusively for the consumption of royal families.  To this day, the Dong Tao Chicken remains a rarity because of the notorious difficulty that is involved in breeding them.

The high demand for the meat of the Dong Tao Chicken in conjunction with its constantly short supply has allowed it, as a commodity, to command an unreasonably high price, with a pair of Dong Taos selling for as high as P2,500USD.

Today, the Dong Tao Chicken is now mostly raised by professional chicken breeders. Still, much like the in the olden times, its meat can only cater to the wealthy who can afford to dine in luxury restaurants where it is almost exclusively served.

3. Damascene Goat

The Damascene Goat, also known as the Damascus Goat, regularly claims the title of “The Most Beautiful Goat” in Middle Eastern goat pageants, which are very popular in the region.  In 2013, the Damascus Goat named Qahr won the prize for the Most Beautiful Goat in the Mazayen al-Maaz competition held in Riyadh.

The Damascene Goat is a breed that is native to the Middle East. Today, it is most prominently raised in Cyprus, Lebanon, and Syria. Sometime in the 19th century, the British introduced the breed to Cyprus where it picked up the name Damascus Goat. The Damascus is so popular a breed that it is prominently referenced in a number of classical works in Arabic Literature.

It is not unheard of for professional goat breeders to breed Damascene Goat specifically for acquiring its many pronounced physical traits. The Damascene Goat is best known for its short and snubbed nose and its undershot jaws. If anything, the physical mutations of the Damascene Goat are rather similar to that of the Bulldog.

The mutation that is responsible for the facial contortions of the Damascene Goat has yet to be fully understood. But apart from its unique cosmetic traits, the Damascene is also a dairy goat breed that is raised by farmers for milk and meat production.

4.  Gibber Italicus Canary

Bird breeding methods, over the years, have progressed to the point where it has allowed breeders to practically control everything about the bird—from shaping their skeletal formation, to manipulating their feather color, density, and softness., to modulating their natural birdsong. The Gibber Italicus Canary is exactly the result of such bird breeding methods.

The Gibber Italicus Canary is a product of intensive close inbreeding efforts made by Italian breeders. Much like most inbred crossbreeds, this canary is prone to inbreeding depression that typically results to a host of health problems, including compromised fertility, high offspring mortality, and a shorter lifespan, among others.

The Gibber Italicus is considered to be among the most fragile canary breed in the world. It is specifically bred by bird hobbyist and breeders who appreciate the Gibber Italicus’ eye-catching humpbacked body, balding head, and skinny profile. To enthusiasts of this bird breed, the ideal Gibber Italicus Canary possesses a figure seven shaped body, long stiff legs, and unfeathered breastbone area,

This strangely appreciated weak and weird appearance of the Gibber Italicus, however, does come with a cost. This canary is notorious for producing offspring that have very low chances of survival, most of which are already dead in the egg.

5. Bubble Eye Goldfish

People have a particularly long relationship with the goldfish. For the longest time, the goldfish has been an aquarium staple. Having been specifically cultivated for purposes of ornamentation, the goldfish has undergone countless crossbreeding that it now comes in different shapes, and sizes—the strangest of which comes in the form of the Bubble Eye Goldfish.

It took many years of selective breeding and genetic tinkering to craft the distinctive appearance of the Bubble Eye Goldfish. The Bubble Eye Goldfish is most recognizably known for its grossly oversized, fluid-filled sacs that bubble under its eyes. These sacs or eye bubbles are known to occasionally deflate, and even burst. Punctured eye bubbles could easily result in injury and infections.

Among those considered as good specimens are with clean, unmarked back, and eye bubbles that closely match, both in color and size. Apart from its distinct eye bubble, the Bubble Eye Goldfish is unmistakable for its malformed, upward-turned eyes, and irregularly curved spine, and lack of dorsal fins. The traits that make the Bubble Eye Goldfish distinctive do not come without a cost, though. This breed of fish is abnormally fragile, even in carefully controlled environments. Their eye bubbles are too delicate to the point that the Bubble Eye should be kept away from moderately aggressive fish.

Through various selective breeding methods, professional crossbreeders have long acquired the ability to pinpoint and encourage specific traits in animals which they find appealing. Conversely, crossbreeding also has allowed us to eliminate specific characteristics in animals that we don’t particularly care for.

Despite the number of widely popular crossbreds, from American bulldogs to Savannah Cats, what remains relatively unknown to many people is the fact that it doesn’t take many qualifications to start messing around with the otherwise natural evolution of animals.