Natural vs. Artificial Selection

Breeding for Specific Traits in Animals and Plants

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Types of corn. US Department of Agriculture

In the 1800s, Charles Darwin, with some help from Alfred Russel Wallace, first came up with and published his "On the Origin of Species" in which he proposed an actual mechanism explaining how species evolved over time. He called this mechanism natural selection, which basically means individuals possessing the most favorable adaptations for the environments in which they lived would survive long enough to reproduce and pass down those desirable traits to their offspring. Darwin hypothesized that in nature, this process would only occur over very long periods of time and through several generations of offspring but eventually, unfavorable characteristics would cease to exist and only the new, favorable adaptations would survive in the gene pool.

Darwin's Experiments With Artificial Selection

When Darwin returned from his voyage on the HMS Beagle, during which he first began formulating his ideas on evolution, he wanted to test his new hypothesis. Since its aim is to accumulate favorable adaptations to create a more desirable species, artificial selection is very similar to natural selection. Instead of letting nature take its often lengthy course, however, evolution is helped along by humans who choose desirable traits and breed specimens possessing those characteristics in order to create offspring with those traits. Darwin turned to artificial selection to gather the data he needed to test out his theories.

Darwin experimented with breeding birds, artificially selecting various characteristics such as beak size and shape and color. Through his efforts, he was able to show that he could change birds' visible features and also breed for modified behavioral traits, much as natural selection might accomplish over many generations in the wild.

Selective Breeding for Agriculture

Artificial selection does not only work with animals, however. There was—and continues to be—a great demand for artificial selection in plants as well. For centuries, humans have been using artificial selection to manipulate the phenotypes of plants.

Perhaps the most famous example of artificial selection in plant biology came from Austrian monk Gregor Mendel, whose experiments with breeding pea plants in his monastery garden and subsequently collecting and recording all of the pertinent data would go on to form the basis for the entire modern field of Genetics. By either cross-pollinating his subject plants or allowing them to self-pollinate, depending on which traits he wished to reproduce in the offspring generation, Mendel was able to figure out many of the laws that govern the genetics of sexually reproducing organisms.

Over the last century, artificial selection has been successfully used to create new hybrids of crops and fruit. For instance, corn can be bred to be larger and thicker in the cobs to increase grain yield from a single plant. Other notable crosses include broccoflower (a cross between broccoli and cauliflower) and a tangelo (the hybrid of a tangerine and a grapefruit). The new crosses create a distinctive flavor of the vegetable or fruit that combines the properties of their parent plants.

Genetically Modified Foods 

More recently, a new kind of artificial selection has been used in efforts to enhance food and other crop plants for everything from disease resistance to shelf life to color and nutritional value. Genetically modified (GM foods), also known as genetically engineered foods (GE foods), or bioengineered foods, got their start in the late 1980s. It's a method that alters plants a cellular level by introducing genetically modified agents into the propagation process.

Genetic modification was first tried out on tobacco plants but quickly spread to food crops—starting with the tomato—and has enjoyed remarkable success. The practice has undergone considerable backlash, however, from consumers concerned with the potential for unintentional negative side effects that may result from eating genetically altered fruits and vegetables.

Artificial Selection for Plant Esthetics

Apart from agricultural applications, one of the most common reasons for selective plant breeding is to produce esthetic adaptations. Take, for example, the breeding of flowers to create a particular color or shape (such as the mind-boggling variety of rose species currently available).

Brides and/or their wedding planners often have a specific color scheme in mind for the special day, and flowers that match that theme are often an important factor in realizing their vision. To that end, florists and flower producers often use artificial selection to create blends of colors, different color patterns, and even leaf coloring patterns to achieve the desired results.

Around Christmas time, poinsettia plants make popular decorations. Poinsettias can range in color from a deep red or burgundy to a more traditional bright "Christmas red," to white—or a mixture of any of those. The colored portion of the poinsettia is actually a leaf, not a flower, however, artificial selection is still used to get the desired color for any given plant variety.