What is Natural Selection?

This evolutionary concept proposed by Charles Darwin explains how species with traits that are helpful in a certain environment have a better chance of surviving and reproducing, transmitting their attributes to subsequent generations and prevailing over other less suitable species.

One of the best-known examples of natural selection is that of the Biston betularia moth; before the Industrial Revolution, its dominant phenotype was a light gray wing color. This shade helped it camouflage itself in the lichens of trees. When the lichens began to darken due to soot from factories, the black moths of this species, which were highly unusual, began to thrive and become more and more common, while the gray ones were less so. The explanation for this is that, while the gene for black wings was recessive, the black Biston betularia had more opportunities in this new environment: their predators could no longer see them as easily, so they started to hunt the gray moths, which were then more visible.

What are the premises of natural selection?

Natural selection, as described by Charles Darwin, had to meet three conditions:

• Phenotypic variability: the existence of different expressions of a certain characteristic; for example, wing color.
• Transmission: if the trait cannot be inherited or replicated, there can be no natural selection or evolution.
• Differential factor for selection: the variation must represent a difference in the crucial question of surviving or not, reproducing or not, in such a way that the individuals that constitute it can continue to propagate. In biology, this is called biological effectiveness.

Natural selection does not necessarily imply an increase in evolutionary complexity, nor does it necessarily lead to innovations; this is because it often acts by suppressing defective variations or eliminating individuals.

The phenomenon of natural selection was first explained in biology; however, the notion of natural selection can be applied in other fields, such as economics, technology, social sciences, and any other case where the three aforementioned principles are met and there is a resulting successful adaptation.

What is adaptation?

Adaptation is the effect of natural selection that allows a species to adapt to the conditions of an environment. Cacti, for example, are plants that are well adapted to places where water is scarce, such as steppes or deserts.

How do adaptations occur?

When a genetic variation appears due to some random change in DNA (mutation), natural selection can lead to a new adaptation. These may be:

• Physiological: when variation affects the functioning of an organism;
• Morphological: when they change form;
• Ethological or behavioral: then there is a change in the behavior of the species.

What other forms of species selection are there?

• Sexual selection: this has been described as another process of genetic selection that occurs not in response to the imperative need for survival but instead to the preference for certain traits in sexual partners. This would explain the development of exaggerated morphologies such as the peacock’s tail, which can serve to attract both the female of its species and any predator with the same effectiveness.

• Artificial selection: an evolutionary process in which humans intervene to develop certain traits in animals and plants, choosing parents with the desired characteristics and subsequently selecting their offspring until they progressively lead to a satisfactory result. Artificial selection has been practiced since the beginning of agriculture to achieve more productive crops; it has also been utilized for the domestication of animals, making them more docile, smarter, more tolerant of certain climates, and so on.