Natural selection, popularized by Charles Darwin, explains how animals change over time as beneficial traits are preserved and negative traits are eliminated. It is only one component of the modern evolutionary synthesis, and is demonstrated by the example of the peppered moth in England. While natural selection alone would suggest species becoming homogeneous, genetic drift and spontaneous mutations prevent this. Darwin’s theory laid the foundation for a more comprehensive set of interconnected theories of heredity.
Natural selection is a theory originally popularized by Charles Darwin. According to this theory, animals in the wild change over time as beneficial traits are preserved and traits that do not advance the species are slowly eliminated. People sometimes confuse this theory with evolution; in fact, it is only one component of the modern evolutionary synthesis that explains how species evolve and change over time.
According to Darwin’s theory, published in 1859 in the Origin of Species, given any animal population, a wide variety of traits can be present. If an animal develops a trait that helps it survive, it will be more likely to pass the trait on to future generations, ultimately resulting in the widespread appearance of that trait as subsequent generations reproduce. This could potentially result in the emergence of an entirely new species over time.
A classic example of natural selection is the peppered moth in England. When the Industrial Revolution happened, huge amounts of coal and other particulates entered the air, blackening the trees around some factories. The white pepper moths stood out starkly against tree trunks, making them easy targets for birds, while the darker moths were able to remain hidden, passing on the genes for dark coloration to future generations because they lived long enough to reproduce. Eventually, the population became predominantly dark, and this process was reversed when England began instituting clean air standards, reducing pollution and allowing trees to revert to a more natural hue that favored pale moths. .
Darwin compared natural selection to the artificial selection demonstrated by humans when they bred plants and animals for beneficial traits. Although Darwin didn’t understand genetics, he knew that people like horse breeders were able to bring out the best traits in successive generations of animals, and that a similar process must occur in nature.
One major problem with natural selection as a standalone theory is that it would imply that species should become homogeneous over time as animals with positive traits dominated the gene pool. As demonstrated by the immense diversity in most species, this is not the case, due to things like genetic drift and spontaneous mutations, which ensure the gene pool doesn’t get too simplistic.
While Darwin’s theory alone was not sufficient to explain the process of evolution, it laid the foundations, and 20th-century scientists built on it in the 1920s to come up with a more comprehensive set of interconnected theories of heredity. Natural selection can be seen at work on many levels, from the development of antibiotic-resistant bacteria to color variations in flowers living in different environments.
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