Artificial selection describes how humans choose organisms with desirable traits and selectively breed them to produce offspring with these desirable traits.
Artificial selection is also known as selective breeding.
Artificial selection differs from natural selection, which is the process that results in the survival and reproductive success of individuals or groups best suited to their environment without human intervention.
Charles Darwin coined the term artificial selection in his famous book “On the Origin of Species.” Darwin had used the artificial selection of birds to gather evidence to explain his theory of evolution. Darwin started to breed pigeons after studying finches on the Galapagos islands to prove his theory. He was able to show that he could increase the chances of desirable traits in pigeons to be passed on to their offspring. Darwin hypothesised that artificial selection and natural selection functioned the same way.
Like natural selection, artificial selection allows reproductive success to individuals with specific genetic characteristics to increase the frequency of desirable traits in the population. Natural selection works because desirable features give the greatest fitness and ability to survive. On the other hand, artificial selection works by selecting traits based on the breeder’s desires. Individuals with the desired trait are chosen to reproduce, and those without the trait are prevented from reproducing.
Fitness is an organism’s ability to survive and pass its genes on to future offspring. Organisms better adapted to their environment will have higher fitness than those not.
The process of artificial selection
Humans control artificial selection as we select what trait is deemed desirable. Outlined below is the general process of artificial selection:
Humans act as the selective pressure
Individuals with desirable phenotypes are selected to interbreed
Desirable alleles are passed onto some of their offspring
Offspring with the most desirable traits are chosen to interbreed
Individuals that display the desired phenotype to the most significant degree are selected for further breeding
This process is repeated over many generations
Alleles deemed desirable by the breeder increase in frequency, and the less desirable traits ultimately can completely disappear over time.
Phenotype: the observable characteristics of an organism.
Humans started selectively breeding organisms long before scientists understood how the genetics behind it worked. Despite this, individuals were often selected based on their phenotypes, so the genetics behind the breeding was not so much needed. Due to this lack of understanding, breeders can accidentally enhance genetically linked traits to the desirable trait, harming the organism’s health.
Fig. 1 - The process of artificial selection
Advantages of artificial selection
Artificial selection brings about several advantages, especially to farmers and animal breeders. For example, desirable traits might be able to produce:
- crops with a higher yield
- crops with a shorter harvest time
- crops with higher resistance to pests and diseases
- reduce costs because farmers can identify crops or animals from their resources to be used
- create new plant and animal varieties
Disadvantages of artificial selection
Despite the advantages of artificial selection, many individuals are still concerned about the practice due to the reasons outlined below.
Reduction of genetic diversity
Artificial selection reduces genetic diversity as only individuals with desirable traits reproduce. In other words, individuals share similar alleles and are genetically similar. Consequently, they will be vulnerable to the same selection pressures, such as disease, which could drive the species into becoming endangered or even extinct.
Additionally, the lack of genetic diversity often leads to the inheritance of adverse genetic conditions. These artificially selected individuals often suffer health conditions and reduced quality of life.
Knock-on effects on other species
If a species is produced that has beneficial traits over another species (for example, a drought-resistant plant), other species in the area could be outcompeted as they have not had their evolution accelerated at the same rate. In other words, surrounding species will have their resources taken from them.
Genetic mutations can still occur
Artificial breeding aims to transfer positive traits from offspring to parents, but poor traits also have the potential to be transferred because mutations are spontaneous.
Mutations are spontaneous changes in the DNA base sequence of genes.
Examples of artificial selection
Humans have been artificially selecting desirable individuals for decades on crops and animals. Let’s look at specific examples of species that have undergone this process.
Crops
Crop yield is increased and improved by breeding crop species with superior results. Artificial selection helps meet the needs of the expanding human population; some crops may also be bred for their nutritional content (e.g., wheat grains) and aesthetics.
Cattle
Cows with desirable features, such as fast growth rates and high milk yield, are selected to interbreed, as are their offspring. These traits are repeated over many generations. As bulls cannot be assessed for milk production, the performance of their female offspring is a marker of whether or not to use the bull in further breeding.
Researchers have found that the selection for high growth and milk yield in cattle is associated with decreased fertility and fitness, leading to lameness. Inbreeding depression is often a consequence of artificial selection, increasing the likelihood of inheriting abnormal health conditions.
Fig. 2 - Cattle that has been selectively bred for its high growth rate
Racehorses
Breeders discovered many years ago that racing horses generally have one of three phenotypes:
All-rounder
Good at long-distance racing
Good at sprinting
If a breeder wants to breed a horse for a long-distance event, they are likely to breed together the best endurance male and the best endurance female. They then allow the offspring to mature and select the best endurance horses to breed further or use for racing. Over several generations, more and more horses are produced that have greater endurance performance.
Differences between artificial selection and natural selection
| Natural selection | Artificial selection |
| Organisms better adapted to their environment tend to survive and produce more offspring. | The breeder selects organisms to produce desirable traits in successive generations. |
| Natural | Man-made process |
| Produces variation | Produces organisms with desired traits and can decrease diversity |
| Slow process | Rapid process |
| Leads to evolution | Does not lead to evolution |
| Only favourable traits are inherited over time | Only selected traits are inherited over time |
Artificial Selection - Key takeaways
- Artificial selection describes how humans choose organisms with desirable traits and selectively breed them to produce offspring with these desirable traits.
- Natural selection describes the process by which organisms with advantageous alleles have an increased chance of survival and reproductive success.
- Charles Darwin coined artificial selection in his famous book “On the Origin of Species”.
- There are both advantages and disadvantages to artificial selection. For example, although artificial selection can increase crop yield for farmers, the process also decreases genetic diversity.
- Examples of artificial selection include crops, cattle and racing horses.
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Frequently Asked Questions about Artificial Selection
What is artificial selection?
The process by which humans choose organisms with desirable traits and selectively breed them in order to produce offspring with these desirable traits. Over time, the desirable trait will dominate the population.
What are some examples of artificial selection?
- Disease resistant crops
- Cattle that produce a high yield of milk
- Fast racing horses
What is the process of artificial selection?
Humans act as the selective pressure.
Individuals with desirable phenotypes are selected to interbreed.
Desirable alleles are passed onto some of their offspring.
Offspring with the most desirable traits are chosen to interbreed.
Individuals that display the desired phenotype to the greatest degree are selected for further breeding.
This process is repeated over many generations.
Alleles deemed desirable by the breeder increase in frequency and the less desirable traits ultimately have potential to completely disappear over time.
What are the common forms of artificial selection?
The common forms of artificial selection include breeding crops to increase crop yield and interbreeding cattle to increase productivity (milk yield and growth rate).
What are the advantages and disadvantages of artificial selection?
The advantages include a higher crop yield, new varieties of organisms can be created and crops can be selectively bred to be resistant to disease.
Disadvantages include a reduction in genetic diversity, harmful knock-on effects on other species and genetic mutations can randomly occur.
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