What is it?
Natural selection is a process by which organisms that are better adapted to their environments produce more offspring to pass on their genetic characteristics. Individuals with more advantageous traits are more likely to survive and reproduce. There are a few different types of natural selection including:
Stabilizing Selection: Here, genetic diversity decreases as the population stabilizes on a particular trait value. For example, robins typically lay four eggs because smaller clutches may result in no viable offspring, while large clutches may result in malnourished chick. A clutch is the number of eggs a bird lays during a single nesting attempt.
Directional Selection: This occurs when a single characteristic is favored in one direction. An example of this is the evolution of the peppered moth in nineteenth-century England. Before the Industrial Revolution, most peppered moths were light in color. But due to the sooty environment, dark-colored moths could better camouflage themselves. Over time, the light-colored moth population was phased out. More recent data indicate that the light form has increased again, following changes in air quality.
Disruptive Selection: Also known as diversifying selection, this method favors extreme characteristics over mild ones. In Galápagos finches, small, narrow bills are specialized for eating soft, tiny seeds, whereas large, deep bills are better suited for breaking tough, hard seeds. Birds with medium-sized bills struggle with both.
Why it matters.
Natural selection is a natural process, but humans have greatly accelerated and redirected it. By altering biodiversity, nutrient cycling, and productivity, we have introduced both benefits and drawbacks.
It is important to recognize that some of our actions have unintended consequences. Size-selective harvesting in fisheries drives fish to mature at smaller sizes and younger ages. Trophy hunting of animals with large horns or tusks reduces the average size of these features over time, since individuals with smaller traits are more likely to survive and reproduce.
On a different note, we have also intentionally benefited from inducing evolution. Farmers have bred crops for higher yields and drought resistance, as seen with corn. Selective breeding has also created the wide variety of dog breeds we know today.
What you can do!
You can help shape how humans understand and respond to natural selection:
- Learn about the impacts of human activity compared to naturally occurring selection and share this knowledge with others.
- Recognize that scientists are still uncovering new details about evolutionary processes.
- Educate yourself about non-native species, which often act as new selective pressures on ecosystems.
Get Involved:
- Support conservation initiatives such as assisted migration, which helps species adapt to new environments.
- Use antibiotics and pesticides responsibly. Overuse kills the most vulnerable organisms and leaves resistant ones to survive and reproduce, creating “superbugs” and resistant pests.
- Volunteer or work with organizations that apply evolutionary principles for conservation and sustainability.
As our understanding of human influence on evolution grows, so does our responsibility to act. Evolutionary thinking already shapes biodiversity conservation, human health, agriculture, and resource management. Looking ahead, there are even greater opportunities to guide evolution in informed, effective, and safe ways.
Information from Science Direct, Biology LibreTexts, NestWatch, NASA Earth Data, Royal Society Publishing, and National Geographic Education.