natural selection

[ nach-er-uhl si-lek-shuhn, nach-ruhl ]
/ ˈnætʃ ər əl sɪˈlɛk ʃən, ˈnætʃ rəl /
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the process by which forms of life having traits that better enable them to adapt to specific environmental pressures, as predators, changes in climate, or competition for food or mates, will tend to survive and reproduce in greater numbers than others of their kind, thus ensuring the perpetuation of those favorable traits in succeeding generations.Compare survival of the fittest.


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Origin of natural selection

First recorded in 1855–60
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023


What is natural selection?

Natural selection is a natural process in which individuals who are better suited to their environment are much more likely to survive and reproduce. As a result, traits or characteristics that help with survival are passed on and become dominant.

Natural selection is best explained with an example situation. Let’s say we have an island full of birds and crickets. The crickets come in yellow, brown, and green. The birds have a harder time seeing the green crickets in the grass and leaves. Because of this, fewer green crickets are eaten by birds, and so they are more likely to live longer to reproduce. The green color has proven to be the best color for survival, and so it will eventually become dominant through natural selection.

In order for natural selection to happen, there must be variety in an environment. In our example, if we only started with yellow crickets and repeatedly only had yellow crickets every generation, we wouldn’t see natural selection. Either all of the crickets would eventually be eaten or they wouldn’t. The crickets themselves would never change.

Natural selection also requires reproduction. If we started with only male green crickets in our example, we wouldn’t see natural selection. Even if all the green crickets lived to old age, they couldn’t reproduce without female green crickets. Without reproduction, the crickets die out.

Finally, natural selection requires traits or characteristics to be inheritable, meaning parents can pass them on to offspring through genetics. In our scenario, if the crickets are unable to pass on their green color, we won’t see natural selection. If cricket color is determined at random rather than through genetics, we will see random increases and decreases of the different colored crickets. Green crickets may live longer, but the color won’t become dominant because green crickets will always have randomly colored offspring.

Why is natural selection important?

The first records of the phrase natural selection come from around 1855. The phrase combines the word natural, which describes something that happens or exists in nature, and selection, a biological term that has to do with a trait of a select group of individuals becoming dominant.

The idea of natural selection was formulated by naturalist Charles Darwin in the 1800s. Darwin used natural selection to help support and explain his groundbreaking theory of evolution. Natural selection, given enough time, will cause advantageous traits to live on in a species. Darwin argued that when stretched over thousands or millions of years, natural selection will eventually lead to a species changing so dramatically that it evolves into an entirely new one. Aquatic animals developed legs and organs that allowed them to survive and thrive on dry land, for example.

The phrase survival of the fittest is no longer used as a synonym for natural selection. Survival of the fittest inaccurately assumes that only beneficial traits can be passed on. In fact, harmful traits can be passed on too. The phrase can also be applied in a way that wrongly assumes that a person’s race makes them superior to another person. Race is no longer considered a scientifically accurate way to categorize human beings.

Did you know … ?

Perhaps the most commonly used explanation and proof of natural selection is the variety of species of finches found on the Galapagos islands. Often nicknamed Darwin’s finches, these multiple species of birds each have noticeably different beaks that allow each species to eat the seeds exclusive to the particular island the bird lives on. According to scientists, it is highly likely each of these species of birds evolved from a common ancestor through natural selection.

What are real-life examples of natural selection?

This video gives a more complex explanation of natural selection and shows a simulation natural selection happening:

In everyday speech, natural selection is often used as a metaphorical reference to the scientific concept. Many non-scientists simplify natural selection as meaning stronger or smarter individuals are more likely to survive.


Quiz yourself!

Which of the following is NOT a major aspect of natural selection?

A. reproduction
B. variation
C. human interference
D. inheritable traits

How to use natural selection in a sentence

British Dictionary definitions for natural selection

natural selection

a process resulting in the survival of those individuals from a population of animals or plants that are best adapted to the prevailing environmental conditions. The survivors tend to produce more offspring than those less well adapted, so that the characteristics of the population change over time, thus accounting for the process of evolution
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for natural selection

natural selection

The process by which organisms that are better suited to their environment than others produce more offspring. As a result of natural selection, the proportion of organisms in a species with characteristics that are adaptive to a given environment increases with each generation. Therefore, natural selection modifies the originally random variation of genetic traits in a species so that alleles that are beneficial for survival predominate, while alleles that are not beneficial decrease. Originally proposed by Charles Darwin, natural selection forms the basis of the process of evolution. See Notes at adaptation evolution. Compare artificial selection.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for natural selection

natural selection

A process fundamental to evolution as described by Charles Darwin. By natural selection, any characteristic of an individual that allows it to survive to produce more offspring will eventually appear in every individual of the species, simply because those members will have more offspring.

notes for natural selection

The expression survival of the fittest was used to describe this process in the nineteenth century but is not favored by modern scientists.
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.