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Introduction

Domestication is an evolutionary phenomenon that is observed over multiple generations occurring artificially with human selection. In the evolutionary phenomenon, humans would selectively choose the favorable offspring of wild plants and animals with behavioral characteristics that are favorable for human use. As a result, phenotypic changes in the species increased the diversity of species but decreased genetic variability. One of the earliest mentions of domestication came from Charles Darwin while observing farmers and animal breeders. Darwin discovered distinctive features and traits in domesticated mammals that were not seen in their wild progenitors. The mammals he observed were more docile and tame, with morphological variation to their ancestors and wild counterparts. The changes were better suited for human consumption and utilization. The domestication of plants and animals rapidly increased the human population and the emergence of modern society.

Background

Domestication is the selection of traits through the influence of reproduction in a group to meet human preferences. This changes the genetic makeup of those species through the entirety of their physical and behavioral appearance which are reflected as domestication syndrome. It was found that the process of domestication dramatically decreases the diversity of gene expression and genomics of wild animals. The change in genes happens throughout the domestication process over the years and can be portrayed as lower adaptability to the natural wild environment or in the genes that code for survival skills in wildlife. Genomics of domestication is used to understand the genetic changes between species over time and further understand what has changed from domestication.

Domesticated species and human history

Dogs

The domesticated dog or Canis lupis familiaris descended from wolves and originated in Eurasia thousands of years ago. The earliest dogs of the New World were not domesticated from North American wolves but most likely came from Siberian ancestry. Genome comparison of wolves and modern dogs suggested that they were domesticated in Asia at least 14,000 years ago, and their lineages continued to split and expand into the hundreds of breeds we have today. Some canine breeds such as the Chow chow or Shiba Inu are more closely related to wolves genetically and these breeds exhibit behaviors similar to their wolf ancestors. Selective breeding has also caused the ‘artificial’ evolution of dogs. Many theories suggest how dogs became man’s best friend. One of the theories suggested that wolves self domesticated themselves by becoming more friendly to humans as means for food. The wolves that were more cordial among hunter-gatherers were at an advantage for survival as food sources became scarce. Another theory suggested that early humans captured wolf pups and domesticated them gradually as pets. The domestication of dogs has changed their phenotypes in many ways, their fur textures and colors, tail length and curvature, eye colors and other facial or body features have distinguishably differed from their wolf ancestors. Caption: Phylogenetic tree of wolves and dog breeds.

Cats

The earliest evidence of cat (Felis silvestris catus) domestication is a burial site of an adult human and a cat found in Cyprus and Egypt, dating back about 9,500 years ago. Evidence suggests that cats self domesticated, living alongside humans for thousands of years before being domesticated. Cats in Ancient Egypt were seen as living embodiments of spirits and were then kept alongside. While few small significant genetic changes have occurred in cats, the presence of a tabby coat is relatively new with genetic evidence suggesting a tabby coat only appeared in the middle ages. Cats migrated along with humans to the northern parts of the continent spreading through Asia and Europe following the migration of humans. Cats would be brought to hunt rodents and help protect food storage.

Cats that were more carnivorous were bred and domesticated. Genealogical confirms this notion as a comparison in the genes of wildcats and cat breeds confirmed that domesticated cats had enriched genes that were involved in lipid metabolization alluding to a carnivorous diet. An allele in the Birman breed had found that genes were associated with behavior and reward in mouse models were present in cats. This finding alludes to domestication syndrome as cats were more subservient to their human owners who would reward them for hunting rodents as they were bred to do so.

Caption: Phylogenetic tree of domesticated felines and wild cats.