Why Are Pets Increasingly Miniature? Artificial Selection Is a Major Cause of Animal Dwarfism

The world is full of wonders, with some people being fat, some being thin, some being tall, and some being short. Some people are surprisingly short, with heights far below average. People with such stature usually suffer from dwarfism. In 'Game of Thrones', the 'Night King' suffers from this disease.

Dwarfism is a genetic disease. Adults generally have a height no more than 4 feet (1.2 meters). Due to various reasons, the secretion of growth hormone is insufficient, leading to stunted growth, with possible disproportionately short limbs, differing slightly from normal children. It can be easily identified with one look.

Dwarfism has both congenital and acquired factors. Although short stature, their intelligence is generally normal.

The Small People Company, with 5,000 people, is open only to people with heights below 4 feet 10 inches (1.47 meters). According to the organization's statistics, approximately 400 dwarf children are born each year.

​However, there are also many miniature animals on Earth. Will there be such diseases in animals?

Animals, especially wild animals, suffer from dwarfism due to genetic mutations is very rare. Generally, it occurs due to two reasons:

1, Island Dwarfism, a natural evolutionary phenomenon that develops miniature individuals for survival;

2, Humans selectively train miniature animals for their own hobbies.

Island Dwarfism

Island Dwarfism is a natural evolutionary process. When an animal lives on an island or in a similar isolated habitat, due to limited resources, the animal's size decreases over several generations. The new species of dwarf leaf chameleon discovered in Madagascar in 2012 is one of them.

To survive in a secluded ecosystem, animals have to adapt to different shapes and sizes.

The two main factors promoting dwarfism in a secluded environment are:

Firstly, limited resources. When an animal is introduced to an isolated environment, such as an island, its ability to develop resources will be reduced, so the animal's breeding rate and size may decrease to cope with limited resources;

Secondly, there may be lack of predators or competition. When an animal in a secluded ecosystem no longer faces threats from other animals, it does not need a large body size, and dwarfism will occur, until it reaches a certain size to balance its energy consumption.

Now, let's take a look at some cases.

Asian Elephant

In 2013, a dwarf Asian elephant was first discovered in the Udatawari National Park in Sri Lanka.

It is an adult male, standing about 1.5 meters tall, with the upper body normal size, and fully developed secondary sexual characteristics. However, its legs are short and thick.

Besides the short legs, this elephant has no differences from other normal-sized elephants in terms of behavior and morphology.

Therefore, not all elephants are gigantic in size.

Seylanese Dwarf Hippopotamus

The Seylanese dwarf hippopotamus is an extinct hippopotamus that lived on the island of Cyprus during the Holocene. Due to dwarfism, it was only 76cm long and weighed about 200 kg.

Ordinary hippopotamuses have a length of 350-450 cm and weigh more than 2 tons, which is heavier than a car.

Miniature Donkey

In 1989, a study described the dwarf donkey found in Jersey, France.

Researchers discovered 36 donkey specimens near a cave. These specimens were very short, and they were 6,000 years ago, the weight reduced to one-sixth of the original weight, from 200 kg to 36 kg. Similarly, the teeth, horns and lower limbs were also smaller.

Besides limited resources and lower predation pressure, sea level rise and geographical isolation also caused dwarfism.

Mazalron, a dinosaur

Mazalron, a dinosaur, is one of the largest terrestrial quadruped dinosaurs on Earth. However, among the many lizard dinosaurs, there is a special Mazalron that suffers from dwarfism.

When comparing tissue samples with larger lizard dinosaurs, researchers found that despite having the basic metabolic rate of the standard lizard dinosaur, Mazalron's growth rate was slower, which indicates that even dinosaurs cannot escape the 'knife and fork' of nature.

Miniature animals bred for pleasure

Besides natural factors, people often selectively breed miniature animals with dwarf phenotypes for their own hobbies. These are typically 'miniature pets' at the genetic level, mainly in dogs, cattle and rabbits. Humans have also created several unique breeds as pets.

For example, Dachshund dogs, miniature horses and miniature donkeys.

Finally

In conclusion, dwarfism is not unique to humans and can occur in animals. However, dwarfism animals in wild animals, observed cases are rare, in contrast, dwarfism animals created for human's pleasure are more common and ordinary.

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