In school, we are taught of how man has evolved over time. We have learnt that our ancestors were apes. But what about the ancestors of our pets? Were the animals that exist today, the same during pre-historic times as well? I have always wondered which animals my pets have descended from. Therefore, in this post I have put forth in brief, the process of evolution of dogs, cats and fish, and also how they came to be adopted as pets, by humans.
It is a fact that most of the breeds of pets that we see today did not exist in ancient times. What we see now is the pedigree version of animals that went extinct thousands of years ago. But how exactly did these new species come into being? Let us have a look.
1. Dog (Canis lupus familiaris)

The dog is said to be the first animal to have been domesticated. All of the people who own dogs must know that they are actually housing a direct descendant of the Grey Wolf. There are two theories regarding how the dog descended from the wolf. One of these theories states that when wolves started to eat the scraps thrown by humans, their fear for each other lessened slowly. Soon, they became friends and some wolves came to be domesticated by man about 10,000 years ago during the Agricultural Revolution. These wolves stayed with humans and experienced a change in their behavior and physical appearance over the years, becoming dogs. Another theory states that some wolves split from their pack and over generations they gave rise to dogs. This happened 32,000 years ago, somewhere in East Asia. After that, the wolf ancestors of the modern dog became extinct.

The behavior of dogs now differs from that of wolves. Dogs are also different from them in form. They are smaller and with shorter muzzles and smaller teeth. But at the molecular level not much has changed. The DNA makeup of wolves and dogs is almost identical. Dogs like Siberian Huskies still hold a resemblance with their ancestors. But that does not hold good for breeds like Pugs, Pomeranians, Poodles etc.This is because they have been selectively bred over the years, to have a change in appearance.

2. Cat (Felis catus)

The house cat is the most popular pet in the world and is found in every place that human habitation exists.The origin of the cat is often debated but it is most commonly suspected that the house cat is a descendant of the wild cat. Some experts thought that the Egyptians were the first to domesticate the cat, some 3,600 years ago. But recent genetic and archaeological discoveries indicate that cat domestication began in the Fertile Crescent of the Middle East, perhaps around 10,000 years ago, when agriculture was getting under way.
According to one of the theories of the domestication of cats, the humans were troubled by the mice that would come and destroy their crops and grains. However, when they found that cats were killing the mice, they thought it would be advantageous if they kept cats in their houses to protect their agricultural produce. So the cats, provided with food and other good things, decided to stay with the humans. Thus they became pets. The house cat of today has not changed a lot from its ancestors. However, it does exhibit a few morphological differences namely, slightly shorter legs, a smaller brain and a longer intestine.

3. Goldfish (Carassius auratus auratus)
Out of all the fish, I have only mentioned the domestication of the Goldfish as it was one of the earliest fish to be domesticated and is one of the most commonly kept aquarium fish. All modern goldfish are decedent from Chinese Crucial Carp. Goldfish domestication started more than a thousand years ago in ancient China as was firmly established by around 1000 AD in the Song dynasty of China. One of the mutations of a Chinese Crucial Carp was found attractive by the humans because that mutation caused the fish to become golden in color. So the humans isolated it and started breeding it more and more to produce numerous goldfish.

Unlike the domestication of other animals, the domestication of goldfish did not occur independently in different places at the same time. It started in China and gradually spread all over. This might have been because the goldfish had very few practical benefits. It was only aesthetically valuable. In some regions only the royal families were allowed to keep these fish as a sign of their magnificence.

As we can see in the above species, aggressive breeding has occurred to make these pets look different from what their ancestors looked like. This process is called artificial selection. Artificial selection is the process by which people choose the traits that they want to see in the animals. It is called artificial because nature does not change these animals but humans change them. When people adopted these animals they favored some attributes of theirs over others and hence used artificial selection to eliminate the unwanted characteristics and add the desired characteristics. Thus they created different varieties of that animal by cross breeding over generations.
Initially in animals like dogs, artificial breeding was employed to make these animals capable of performing certain tasks. But later on it was used only to alter the appearance of dogs, cats and also fish, so that they would become more appealing. The traits that were passed on to the animals may or may not be beneficial to those animals but that does not stop people from trying it out. Often it results in sicknesses and genetic diseases getting amplified in these poor animals. So they have health problems and are not as healthy as their ancestors were. Aggressive breeding can produce animals that are attractive enough to win shows but those animals will lead lives of illness and suffering. So let us not be selfish. Let us do for our pets what is in their best interest.

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