Artificial selection: what it is, types, and how it works

The world is inhabited by approximately 7.7 billion inhabitants, of which (according to the World Health Organization) 690 million went hungry during 2019. It is a fact that global production and distribution of goods is completely skewed because, on the other side of the coin, 1.9 billion people were overweight in 2016.

The numbers in terms of population are advancing at a dizzying rate and, unfortunately, food production chains are increasingly seen threatened by multiple processes: multi-resistant bacteria, lack of space, climate change and many other deleterious events for livestock and farming. It is reasonable to think, therefore, that the "natural" characteristics of the beings we feed on are no longer sufficient.

Here terms like genetic engineering and artificial selection come into play. The human being has modified or selected the genes of various species of living beings of agricultural, livestock interest or any animal with social interest (pets, pack animals, etc.) for their own benefit throughout history: we are not facing a new practice, but we are facing an increasingly aggressive expansion of the herself. If you want to know more about artificial selection and what it entails, keep reading.

• Related article: "The theory of biological evolution: what it is and what it explains"

What is artificial selection?

It is common for society to fear the "ghost" of change, because playing at being gods can seem dangerous in a world in which we have much to know. The reality is that, for better or for worse, humans have strayed from natural mechanisms for hundreds and hundreds of years.

To understand what artificial selection is, the first thing to clarify is what it is not, since it is It is common to attribute biased characteristics to these types of terms according to the argument that is being wield. With all the care in the world and leaden feet, we confront the term of artificial selection with others related to it in the following lines.

Artificial selection VS natural selection

Natural selection is defined as the evolutionary mechanism based on the differential reproduction of genotypes in a biological population.. Postulated by the famous biologist Charles Darwin, natural selection postulates that environmental conditions (whether biotic or abiotic, that is, from the physical environment or caused by other living beings) favor or hinder the reproduction of species according to their quirks.

It is necessary to know that natural selection is not an infallible and perfect mechanism: living beings do what they can with what they have, which is why not all adaptations are the best in a medium dice. In summary, all this evolutionary force is based on fitness: the living beings that present the most suitable characteristics in a given environment will live longer and, therefore, reproduce more and transmit their genes to the following generations.

It is also important to note that natural selection is not a unique force, since evolution it is also biased by processes such as genetic drift, which are completely random and of a nature stochastic.

On the other hand, artificial selection, as its name suggests, does not respond to normal adaptive mechanisms in a wild environment. We are facing an environment of everything but natural, since it is characterized by developing in a widely anthropized environment where we choose what interests us, human beings.

Artificial selection VS genetic engineering

It is very common to observe a clear confusion regarding these two terms. It is time to define them both quickly and concisely so as not to leave room for doubt.

Genetic engineering can be summarized in the following concept: a discipline that encompasses a series of techniques that involve the direct modification of the genes of an organism for a specific purpose.

On the other hand, artificial selection, worth the redundancy, is the selection of parents with one (or more) characters of interest, so that all possible descendants also present them and spread the trait in the population wanted.

It is shocking to know that, to this day, only 27 types of transgenic crops are marketed and 95% of genetically modified animals are laboratory rats for purely scientific purposes. The reality is that most of the food that ends up on our table is the product of artificial selection and not engineering genetics, since obtaining a transgenic animal is costly, difficult and, today, an uncommon practice in the field rancher.

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Types of artificial selection

As you may have observed, there is a clear attribute that differentiates artificial selection from the rest of the mechanisms: here the human being chooses the best of what is already available, since he does not create new traits where before there was no indication of them.

Thus, when we speak of a hen that lays many eggs, we are referring to the product of an extensive history of selection. artificial where each time the most suitable laying parents have been selected, not from a transgenic animal that has undergone a modification genetics. It is very important to make this distinction because, although the term "transgenic" is fashionable, it is not at all as widespread as many people think.

Once we have left this forest of terminological doubts, it is also necessary to emphasize that there are several types of artificial selection. Based on the degree of planning of the same, there are two types:

• Conscious: when it responds to a selection plan, designed and executed at will, to preserve certain traits above others in a domestic species.
• Unconscious: when it occurs accidentally, responding to criteria not planned in advance (or at least not formalized).

A clear example of conscious selection that is self-explanatory is that of dogs: breeds are the product of interbreeding and inbreeding, where the individuals of interest are selected for sexual reproduction by means of a criterion specific. On the other hand, and without leaving the world of canids, the case of black wolves could be considered as an unconscious artificial selection.

According to scientific sources, these black wolves belong to the same species as the gray wolves of all life (Canis lupus), but it is speculated that its melanistic color arose from crossing with domestic dogs that carried this gene. Thus, in this case, the human being would be making an unconscious artificial selection: the characteristics of an animal population are indirectly (and unintentionally) modified.

On the other hand, artificial selection can also be divided according to what is sought (or not) in the population of interest:

• Negative selection: prevent specimens from being born with characteristics that are not desired.
• Positive selection: favor the reproduction of certain living beings with the desired characteristics.

In our minds, we tend to think of positive selection when talking about artificial selection: we choose the largest tomatoes, the hens that lay the most, the cows with the most meat and muscle. The reality is that a farmer, when he euthanizes an animal with a genetic dysfunction, is already inadvertently performing negative artificial selection. It is much more common to select living beings based on what is not wanted (diseases, birth defects and other events) than to choose them for their positive attributes.

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Benefits and harms of this procedure

We cannot close this space without the obvious ethical connotations that artificial selection carries with it. Among the clearest benefits of these techniques we can find the following:

• Artificial selection allows a more harmonious coexistence between domestic species and human society.
• Production capacity can be increased with the same space and number of individuals.
• Sometimes artificial selection allows the permanence of certain species over time, since they are in a controlled environment.

On the other hand, the disadvantages of all this are also more than clear: sometimes some populations become the shadow of what they were in their wild environment. Excessive inbreeding, for example, leads to a weakening of the genetic lineage of the species and its evolutionary destiny.: The descendants of this type of selection are more prone to certain diseases, anatomical difficulties, unpredictable mutations and a host of other problems. The reality is truly uncomfortable, as it is clear that a pug will never have the same health and evolutionary fitness as a wolf.

And you do you think?

As you may have read in these lines, we are facing a very thorny issue. It is clear that artificial selection entails multiple ethical dilemmas, since when is the modification of a species unjustifiable? To what extent can the evolutionary cord be tightened without breaking it? What is the limit of animal suffering that we are willing to promote in order to increase productivity?

All these questions depend on the judgment and values ​​of each and every one of the readers who have traveled these lines. There is no definitive answer, but one thing is clear: we are more and more people on the planet, and nature is no longer able to supply us. What to do from here is subject to personal judgment.

Bibliographic references:

• With increasing hunger and the persistence of malnutrition, achieving zero hunger by 2030 is doubtful, warns a report from the United Nations, World Health Organization. Picked up on December 13 in https://www.who.int/es/news/item/13-07-2020-as-more-go-hungry-and-malnutrition-persists-achieving-zero-hunger-by-2030-in-doubt-un-report-warns#:~:text=En%20la%20%C3%BAltima%20edici%C3%B3n%20de, 60% 20million% 20en% 20five% 20a% C3% B1os).
• Artificial selection, undestandingevolution. Picked up on December 13 in https://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_30_sp
• Lungarete, F. (2012). Artificial selection (Doctoral dissertation, National University of La Plata).
• Soler, M. (2002). Evolution. South Editions Project: Granada.