79 Artificial Selection, Natural Selection, and Biological Fitness
Jung Choi; Mary Ann Clark; and Matthew Douglas
Artificial Selection
Artificial selection is the process by which humans intentionally breed plants, animals, or other organisms to enhance desirable traits. Unlike natural selection, which occurs without human intervention, artificial selection involves choosing specific individuals with preferred characteristics—such as size, color, yield, or behavior—and breeding them to amplify those traits in future generations. This practice has been fundamental in agriculture and animal husbandry, enabling the development of crop varieties with greater resistance to pests, livestock with higher productivity, and domesticated animals with favorable temperaments. Over time, artificial selection can lead to significant genetic changes, sometimes resulting in organisms that are vastly different from their wild ancestors. However, this process can also reduce genetic diversity, which may make populations more susceptible to diseases and environmental changes.
Charles Darwin used the concept of artificial selection as a framework to understand natural selection. Observing how humans selectively bred plants and animals for desirable traits, Darwin saw parallels in how nature might also “select” traits that enhance survival and reproduction. For example, just as breeders choose animals with favorable traits to pass on to offspring, Darwin hypothesized that environmental pressures could act similarly, favoring organisms with traits that help them thrive. He recognized that, unlike artificial selection, where humans intentionally select specific traits, natural selection operates unconsciously, driven by environmental factors and survival challenges. By studying the effects of selective breeding on species over generations, Darwin developed insight into how small, gradual changes in natural populations could accumulate, eventually leading to the formation of new species. This analogy helped him articulate the principles of evolution and argue that nature itself could shape life over time through selective pressures similar to those seen in domestication.
Natural Selection
Thomas Malthus, an English economist and scholar, authored An Essay on the Principle of Population in 1798, which examined the potential consequences of rapid population growth in relation to limited resources. Malthus argued that populations tend to grow exponentially, while food resources increase arithmetically, creating an inevitable strain as resources become insufficient for the growing population. He suggested that this imbalance would lead to competition for survival, with some individuals naturally struggling more than others to obtain the resources needed to live. Charles Darwin found profound inspiration in Malthus’s ideas when developing his theory of natural selection. Darwin realized that, much like human populations, all species produce more offspring than can survive, leading to a constant struggle for resources. This struggle, he reasoned, would favor individuals with traits that offered survival advantages, allowing them to outcompete others, survive, and reproduce. Thus, Malthus’s work helped Darwin understand how natural selection operates within populations, shaping species over time in response to environmental pressures.
Biological Fitness
Biological fitness, is a measure of an organism’s ability to survive, reproduce, and pass its genes to the next generation in a particular environment. Fitness isn’t about physical strength alone; rather, it encompasses an organism’s overall adaptability to its surroundings. Those with higher biological fitness possess traits that give them an advantage in survival and reproduction, allowing them to contribute more offspring to the population. These traits might include physical characteristics, behaviors, or even biochemical efficiencies that enhance survival odds in specific ecological contexts. Over generations, these advantageous traits become more common, as natural selection favors individuals who are best adapted to their environment. Therefore, biological fitness drives evolution, shaping species to better fit their ecological niches and enhancing population resilience over time.
