Long before DNA unraveled the double helix of life, scientists were already tinkering with its inheritance. The idea that traits could be passed from one generation to the next fascinated early naturalists. So, they began testing it the only way they could — by breeding plants and animals, watching what happened, and doing it again. This ancient curiosity gave rise to a powerful tool: artificial selection.
Also known as selective breeding, artificial selection is the human-guided cousin of evolution by natural selection. Instead of letting nature decide who reproduces, we do. Whether cultivating corn with plumper kernels or breeding dogs with specific skills, we nudge life’s genetic trajectory to suit our own ends.
Through generations of careful choice — favoring this cow over that one, this tomato over that vine — we’ve shaped everything from the foods we eat to the companions we cherish. The results are often striking. A Chihuahua and a Great Dane share a common wolf ancestor, yet selective breeding has pulled them worlds apart in form and function.
It was this human-driven tinkering with traits — selecting the fastest horse, the sweetest fruit, the most obedient dog — that gave Charles Darwin a crucial clue. If humans could mold species over generations, could nature be doing something similar, only on a much grander scale?
Natural selection versus artificial selection
Natural selection, a fundamental pillar of evolutionary theory, is a process through which populations of organisms undergo adaptation and transformation. In essence, this process favors individuals endowed with advantageous traits for survival and reproduction, ensuring their greater likelihood of passing on genes to successive generations. This concept is succinctly encapsulated as the “survival of the fittest”. Unlike artificial selection, this is a natural process wherein the environment exerts selective pressure on the organisms leading to speciation.
Darwin drew parallels between natural selection and artificial selection. He was inspired by the evolution observed in pigeons bred as a hobby in England. Due to this inspiration, he recognized that the principles underlying artificial selection could be applied to explain the process of natural evolution. In both cases, the differences in survival and reproduction success of individuals based on their traits led to changes in populations over time, driving evolution.
Darwin’s appreciation of selective breeding served as a bridge between human-driven interventions and natural phenomena.
The Origins of a Theory
It’s hard to overstate how much Charles Darwin leaned on artificial selection to shape his theory of natural selection. In his legendary book, On the Origin of Species, Darwin drew a compelling analogy between the pigeon breeders of Victorian England and nature itself. Just as a breeder might favor birds with fancier tails, nature, through environmental pressures, favors traits that offer an edge in survival or reproduction.
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Take the finches of the Galápagos Islands — a classic tale. Though Darwin didn’t obsess over them as deeply as later textbooks suggest, their diverse beak shapes became an enduring metaphor for his big idea. Each beak, tuned to crack a specific seed or sip from a certain flower, hinted at nature’s quiet sculpting over time.
These variations were not arbitrary but more so finely tuned adaptations to the available food sources in the environment. Darwin recognized that beak morphology affected the finches’ ability to survive and thrive in their respective habitats and thus, the concept of natural selection was born.
However, Darwin didn’t have the last word on evolution. In fact, evolution is still a very active field of research, and new (surprising) findings are still coming in.
Natural Selection Could Slow Evolution
But here’s where things get more interesting. In a 2023 study published in New Phytologist, researchers from Michigan State University led by Jeff Conner proposed a twist: natural selection doesn’t always accelerate evolution. Sometimes, it slows it down.
“We’re suggesting that selection can also slow things down, that it can cause similarities as well as differences,” said Conner in his interview with the US National Science Foundation.
“Perhaps the best method to test for short-term constraints is artificial selection because if a trait responds to artificial selection, it clearly can evolve,” the team added. “But if the trait does not respond, there is a constraint caused by a lack of genetic variation.”
The team studied the length of the stamens or pollen-producing parts of wild radish, wherein two of its six stamens are short while the remaining four are long. Interestingly, this trait was found to be widespread among nearly 4,000 relatives of the wild radish.
To investigate the influence of selection, they employed artificial selection, selectively breeding wild radishes with stamens closer in length, aiming to alter this characteristic. The results were remarkable and not only did the trait respond to selection, but the team also managed to narrow down the difference in stamen length by over 30%.
Researchers believe that the differences in stamen length gives the species an advantage when it comes to pollination syndromes, but they aren’t sure exactly what that advantage is. Nonetheless, this study demonstrates that selection can also slow evolution and maintain similarities throughout generations.
Humans Are Genetic Tinkerers
The power of artificial selection is most evident in agriculture. Thousands of years ago, humans began selectively breeding a wild mustard plant, Brassica oleracea. The result? Broccoli, cabbage, kale, cauliflower, and kohlrabi — all from the same ancestral weed. By focusing on traits like leafiness, flower sterility, or stem swelling, farmers sculpted entirely new vegetables.
Artificial selection in plants aims to seek enhanced traits such as yield, pest resistance, nutritional content, and adaptability to changing environmental conditions. Selective breeders utilize techniques such as crossbreeding, hybridization, and genetic engineering.
One of the most popular examples is the selective breeding of wild mustard which resulted in five distinct staple vegetables like cauliflower, broccoli, cabbage, kale, and kohlrabi. All these greens bear little to no resemblance with the wild mustard, Brassica oleracea. For example, the emergence of kale resulted from the preference and selection of mustard plants with larger leaves. Cauliflower, on the other hand, was cultivated through the selection for sterile flowers, while cabbage was developed by choosing plants with a specific internode length, leading to a shorter distance between leaves.
Selective breeding of wild mustard led to five distinct crops. Photo credits: Pat Holroyd (for the wild mustard) and Helina Chin (for the cauliflower, broccoli, cabbage, kohlrabi, and kale)
In animals, the process is just as transformative. Domesticated dogs exploded in variety thanks to selective breeding for size, behavior, and looks. Herding breeds like the Border Collie are tuned for agility and intelligence. Meanwhile, guard dogs like the Dogo Argentino were bred for strength and loyalty.
Other artificial selection examples
- Wheat varieties with disease resistance, higher yields, and desirable baking qualities
- Corn varieties that have improved kernel size, sweetness, and resistance to pests.
- Roses were selected for traits such as color, fragrance, and petal arrangement.
- Cattles have been selectively bred aimed at improving meat and milk production. Different breeds like Angus for beef and Holstein for milk were a result of artificial selection.
- Horses were also selectively bred to be tailored for specific tasks. For instance, Thoroughbreds were selected for horse racing and other equestrian sports.
Corn varieties as a result of artificial selection. Image credits: LoggaWiggler/Pixabay.
Artificial selection may lack the grandeur of glaciers or the violence of extinction, but it’s no less a force of evolution. It’s a quiet, methodical kind of power — one rooted in gardens, barns, and laboratories. As we continue to shape life, we should remember that evolution isn’t just something that happens to us. It’s something we do.
