Animal Domestication: An Evolutionary Process with Human Intervention

INTRODUCTION

Evolution by means of natural selection is an astounding systematic process discovered by Charles Darwin. Charles Darwin founded his theory of evolution by natural selection by observing finches in the Galapagos Islands, this is a well-known fact. His theory is commonly found to be broken down into four statements that everyone can understand. According to Charles Darwin’s theory of evolution, each generation produces more individuals that are more apt to survive. The physical appearances vary among the new generations and can be passed onto the next.

Individuals with better heritable traits based on the surroundings will be more likely to survive. Finally, a new species will eventually come to be when reproductive isolation occurs.

As biologists, all of the previous information is well known and taught in almost every beginner’s biology course. However, a topic that is not discussed quite as much or as in depth is artificial selection. Artificial selection, simply put, is evolution by natural selection but with human interference.

It is also commonly known as human selective breeding. Humans are particular beings and like things to be made in favor of making their lives easier. So at some point in history, humans began to do their own alterations to animals to make their lives better in one way or another. Thus making humans the selecting agent within the artificial selection process that leads to the evolution of a species that may not have evolved on its own.

The process of human selective breeding is usually only used for four main purposes.

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Those purposes are to breed animals for research, usable products or services, conservation reasons, or just as pets (Flint and Woolliams 2008). The repeated selective breeding done by humans eventually leads to the domestication of animal species that we breed for the listed purposes. Domestication can be found among all types of animals and insects, plants, and even bacteria. Domesticated individuals have slowly been integrated into the human economy or society over many years. The domesticating of different species may only increase in time due to the increased technology capabilities of humans (Zeder 2012).

This paper will go further in depth of some very common domesticated animal species to hopefully gain a better understanding of selective breeding and domestication. With each animal species, the supposed areas that started domesticating the species and why the species was utilized by humans will be discussed.

DOMESTICATION OF DOGS

Many people grew up being taught that dogs are domesticated wolves and have been bred into the variety of dog breeds that there are today. Genetic comparisons among many dog breeds, wolves, jackals, and other canids have shown that dogs share genetic sequences closest to the wolves. However, the temperament of modern wolves makes it hard for many researchers to believe that people back in that time were able to tame the wolves. Recent studies have shown that wolves are still unable to take commands as well as dogs at young ages (Pennisi 2002). So even though the possibility of dogs being descendants of wolves is high there is still more research that needs to be done to conclude this hypothesis.

There have been further studies done to try to pin point the origin of dog domestication too. As stated previously, study results lean towards dogs being descendants of wolves. Some researchers believe to have it narrowed down specifically to gray wolves from the Holarctic area. If that truly is the case then dogs had to have crossed the Bering Strait from the old world in order to evolve and be domesticated in the new world or they evolved and were domesticated independently. Either way, chances are that Native American dogs reproduced with the evolved dogs brought over from Eurasia leading to the great variety of breeds there are today (Leonard et al. 2002). It is also theorized that dogs were traded or were travel companions with humans across the new world, Europe, and Asia which would allow for the genetic variety of the new and old world dogs to mix and create even more new breeds.

Now that the dog’s origin and possible upbringing possibilities have been covered it is time to look into how dogs were possibly domesticated and bred for specific selections. Unlike common belief, there is research that shows humans may not have been as directly involved in domesticating dogs as most believe. This research instead says that it is more likely that dogs of the past were still capable of breeding with their wild relatives and were not genetically or physically separated as many used to think. It also shows how human interference for selective breeding may not have been as popular towards the beginning of domesticating dogs as it is now (Marshall et al. 2014).

Who knows, the ancient dogs could have begun the domestication process more or less on their own to benefit themselves. Their association with humans would have allowed for earlier reproduction opportunities, a decrease in needing to be on the run, and they could be more social than their more wild relatives.

DOMESTICATION OF CATS

The domestication of cats has been theorized to have begun either in Europe or Asia after the domestication of dogs in the Fertile Crescent. The domestication of cats is not quite as glamorous or complicated as the dogs and was not commonly seen until settlements and farms were established. Since cats are pretty much the opposite of dogs, it is believed that wild cats intruded into houses or barns for shelter and to catch any mice running amuck and the humans allowed it since the wild cats did no harm to them (Driscoll et al. 2007). Over time the once wildcats became more docile and tolerable of humans.

Interestingly enough, there is a theory that the domestication of wildcats is not quite complete. This theory comes from the fact that more than ninety-seven percent of all domestic cats do not depend on human-controlled breeding. Many of those cats are feral and reproducing with the mates they choose, whether the mates are feral too or domesticated. Charles Darwin felt it was needed to look at the difference between wildcats and domesticated cats. His research found that the main difference is domesticated cats have a longer intestine than wildcats. The longer intestine probably compensates for any human scraps domesticated cats gets rather than a more strict carnivorous diet like wildcats. This discovery made Darwin think that cat domestication is less than two hundred years old and may still be in the works (Driscoll et al. 2009). Only time will tell if Darwin’s theory of cat domestication is correct.