Genetic Preference by Humans: The Process of Choosing Favored Traits
Artificially played God in the way-back days, tinkering with life's damn fine inheritance. Fascination for the inheritance of traits led early naturalists to experiment, breeding plants, and animals to see what stuck. This old-school curiosity gave birth to a powerful tool: selective breeding.
Known by another name, artificial selection, this bad boy is the with-a-little-help-from-us cousin of evolution by natural selection. Instead of letting Mother Nature pick the winners, humanity does. Whether it's growing plumper corn kernels or training dogs for certain skills, we nudge the genetic trajectory of life to make it more useful to us.
We made careful choices over generations – preferring one cow over another, one tomato over another vine – to sculpt everything from the foods we eat to the companions we treasure. The results were striking. A Chihuahua and a Great Dane share a common ancestor, yet artificial selection pulled them as far apart as night and day in form and function.
It was this human-driven fiddling with traits – selecting the fastest horse, the sweetest fruit, the most obedient dog – that gave ol' Charles Darwin a damn good clue. If humans could mold species over generations, was it possible that nature was doing something similar on an even grander scale?
Natural selection or artificial fiddling?
Natural selection, a bedrock principle of evolutionary theory, is a process that drives populations of organisms to evolve. It involves favoring individuals endowed with advantageous traits for survival and reproduction, ensuring a greater likelihood of passing on genes to succeeding generations. Essentially, "the survival of the fittest" means the best-equipped individuals are better suited to cope with their environment. Unlike artificial selection, this is an all-natural, no human intervention process – the environment puts the selective pressure on the organisms, leading to speciation.
Darwin compared natural selection to artificial selection. He found inspiration in the evolution he observed in pigeons, which were bred as a hobby in England during his time. He recognized that the principles governing artificial selection could be applied to explain the process of natural evolution. In both cases, the difference in survival and reproduction success of individuals based on their traits led to changes in populations over time, driving evolution.
Darwin's stroke of genius
In his landmark book, On the Origin of Species, Darwin drew a compelling analogy between selective breeders and nature herself. Just as a breeder might favor birds with fancier tails, nature, through environmental pressures, favors traits that give an edge in survival or reproduction. The finches of the Galápagos Islands became a classic metaphor for Darwin's idea. Beak shapes, adapted to crack specific seeds or sip from certain flowers, hinted that natural forces subtly shaped life over time.
Natural selection: speeding up or slowing down?
A 2023 study in New Phytologist flipped the script a bit: natural selection might not always speed up evolution. Sometimes, it might slow things down.
"We're suggesting that selection can also slow things down. It can cause similarities as well as differences," said Jeff Conner in an interview with the US National Science Foundation.
Researchers studied the length of the stamens in wild radish, where two of its six stamens are short, and the remaining four are long. They found that this trait was widespread among nearly 4,000 wild radish relatives. By employing artificial selection, they narrowed the difference in stamen length by over 30%.
The team believes that differences in stamen length could provide an advantage for pollination syndromes but aren't sure exactly what that advantage is. Nevertheless, this study shows that selective pressures can work against evolution, too.
Human: adaptable genetic tinkerers
Artificial selection is most evident in agriculture. Thousands of years ago, humans began selectively breeding a simple wild mustard plant, Brassica oleracea. The result? Award-winning veggies like broccoli, cabbage, kale, cauliflower, and kohlrabi – all from the same damn weedy ancestor. By focusing on traits like leafiness, flower sterility, or stem swelling, farmers cleverly reshaped the humble mustard into diverse crops.
In animals, artificial selection has been instrumental in creating an array of domesticated breeds. Dogs, for instance, bloomed into a multi-faceted family with distinct sizes, temperaments, and appearances as a result of selective breeding for specific tasks. Herding breeds like Border Collies were tuned for agility and intelligence, while guard dogs like the Dogo Argentino were bred for strength and loyalty.
Other instances of artificial interventions
- Wheat varieties with disease resistance, high yields, and attractive baking qualities
- Corn varieties boasting larger kernels, enhanced sweetness, and improved pest resistance
- Roses selected for stunning color, alluring fragrance, and unique flower shapes
- Cattle with augmented milk and meat production, including breeds like Angus for beef and Holstein for milk
- Horses bred for their prowess in horse racing and other equestrian sports, like the Thoroughbred
Artificial selection may lack the panache of plate tectonics or the drama of extinction, but it's a powerful force of its own, silently at work in gardens, barns, and labs. As we continue to tinker with the genetic machinery of life, let's remember that our actions can drive evolution. Evolution isn't just something that happens to us; it's something we do.
- agriculture
- animal breeding
- artificial selection
- Brassica oleracea
- Darwin's finches
- evolution
- evolutionary biology
- genetic constraint
- genetics
- Galápagos Islands
- natural selection
- plant breeding
- selective breeding
- wild radish*
- Artificial selection, a form of manipulation inspired by evolution, has significantly impacted various aspects of life, including agriculture and animal breeding, contributing to the development of diverse crop varieties and animal breeds.
- Through selective breeding, humans have reshaped the humble mustard plant, Brassica oleracea, into numerous award-winning vegetables such as broccoli, cabbage, kale, cauliflower, and kohlrabi.
- Artificial selection has also played a crucial role in creating distinct dog breeds, with herding breeds like Border Collies developed for agility and intelligence, while guard dogs like the Dogo Argentino were bred for strength and loyalty.
- By scrutinizing the length of stamens in wild radish and employing artificial selection techniques, researchers have shown that selective pressures can work against evolution as well, causing similarities among species rather than differences.
- The effects of artificial selection can be observed in various instances, such as the development of wheat varieties with enhanced disease resistance, high yields, and attractive baking qualities, and the breeding of horses for horse racing and equestrian sports, like the Thoroughbred.
