- Domestication of Dogs
- Examples in Agriculture
- Disadvantages of Selective Breeding
Selective breeding, also known as artificial selection, is a process used by humans to develop new organisms with desirable characteristics.
In selective breeding, a breeder chooses two parents with beneficial phenotypic traits to reproduce, yielding offspring with those desired traits. Selective breeding can be used to produce tastier fruits and vegetables, crops with greater resistance to pests, and larger animals that can be used for meat.
The term “artificial selection” was coined by Charles Darwin, but the practice of selective breeding predates Darwin by thousands of years. In fact, selective breeding is one of the earliest forms of biotechnology, and it’s responsible for many of the plants and animals that we know today.
What Is Selective Breeding?
Selective breeding is a process in which humans breed specific parents to create offspring with desirable characteristics. Examples include dogs bred for specific work tasks or fruit bred to be sweeter.
Domestication of Dogs
One of the earliest examples of selective breeding is the domestic dog (Canis familiaris), which humans have been breeding for at least 14,000 years.
Scientists believe that the domestic dog evolved from the wild gray wolf (Canis lupus), and through artificial selection, humans were able to create hundreds of different dog breeds.
As people domesticated and bred dogs over time, they favored specific traits, like size or intelligence, for certain tasks, such as hunting, shepherding, or companionship. As a result, many dog breeds have vastly different appearances. Think of the Chihuahua and the Dalmatian — they’re both dogs, but they share few physical attributes. This degree of difference in a single species is a unique phenomenon in the animal world.
Examples in Agriculture
Selective breeding has also been practiced in agriculture for thousands of years. Almost every fruit and vegetable eaten today is a product of artificial selection.
Vegetables Derived from Wild Cabbage
Cabbage, broccoli, cauliflower, Brussels sprouts, and kale are all vegetables derived from the same plant, Brassica oleracea, also known as wild cabbage. By isolating wild cabbage plants with specific characteristics, farmers were able to create a variety of vegetables from a single source, each with different flavors and textures.
Broccoli, for example, was developed from wild cabbage plants that had enlarged flower development while kale was derived from Brassica oleracea with larger leaves.
The Development of Corn
Corn, or maize, is an unusual product of selective breeding. Unlike rice, wheat, and cabbage, which have clear ancestors, there is no wild plant that looks like corn.
The earliest records of maize indicate that the plant was developed in southern Mexico 6,000-10,000 years ago from a grass called teosinte. Scientists believe that early farmers selected only the largest and tastiest kernels of teosinte for planting, rejecting punier kernels.
This process allowed the farmers to develop corn very quickly, as small changes in the plant’s genetic makeup had dramatic effects on the grain’s taste and size. Despite their physical dissimilarities, teosinte and corn only differ by about five genes.
Today, corn is a staple in diets across the world. Averaged over the years from 2012 to 2017, 986 million tons of maize was produced each year around the world, primarily in the United States, China, and Brazil.
Disadvantages of Selective Breeding
Without selective breeding, many of the plants and animals on earth today would not exist. However, there are some disadvantages of artificial selection, especially in the case of inbreeding.
Through inbreeding, two closely related organisms reproduce to yield a purebred with desired traits. However, these organisms may also have undesirable traits due to recessive genes found in both parents. Thus, purebred dogs are sometimes born with health defects like hip dysplasia and have shorter life spans than other mixed-breed dogs.
