Facts and Myths about Evolution
Understanding Darwin's Great Idea: Evolution by Natural Selection
Sep 14, 2009
February 12, 2009 was celebrated around the world as “Darwin Day”: the two hundredth anniversary of the birth of Charles Darwin, the author of one of the most influential books in science, On the Origin of Species. In this book, Darwin explained how species change over time in a clear, testable way.
However, for many people, confusion reigns about evolution. A startling number of Americans – 45% of the population of the United States – do not think that new species of plants and animals have arisen from other species (Harris Poll, 2005). An even greater percentage of Americans (54%) do not think that evolution resulted in the human species. A lack of understanding about the process of evolution is probably at the root of this confusion, given that acceptance of evolution is positively correlated with education level, as shown by a 2006 Gallup Poll.
How Evolution by Natural Selection Works
Evolution by natural selection is deceptively simple. Four simple observations about plants and animals led Darwin to propose natural selection:
- First, resources that organisms need to survive, such as food and shelter are not infinite.
- Second, organisms tend to produce many offspring.
As a consequence of these two facts, there will be competition for these limited resources, and not all of these offspring will survive to reproduce. Darwin termed this the “struggle for existence”.
- Third, all members of a species are a bit different from one another, and these differences are primarily inborn (due to one’s genes).
- Fourth, some organisms within a species are better at taking advantage of particular resources than others, a fact that has been termed “survival of the fittest” (for example, a tree might exhibit deeper roots than other members of its species, enhancing its ability to gather water and minerals from the soil).
Based on these observations, Darwin reasoned that an organism’s chances of survival in its environment are due to that organism’s “particular characteristics” (what are now known to be genes), and therefore the organism would pass its advantageous traits on to its own offspring. Due to these advantageous traits, the offspring would be more likely to survive to adulthood and reproduce (“natural selection”). Hence, such traits would become more common in the population over time, leading to wholesale change of the species. This change over time was originally termed “descent with modification” by Darwin, but is now generally called “evolution by natural selection”.
Myths About Evolution
In spite of the clarity of Darwin’s hypothesis, grave misconceptions about evolution have persisted to the present day. For example, it is important to understand that “survival of the fittest” means only that organisms that are best suited for their particular environment are the most likely to live long enough to pass on their genes to the next generation. Such organisms may not be the biggest, fastest, or strongest; the suite of characteristics that happen to be advantageous depends on the environment in which the organisms live.
References
Darwin, C. 1859. On the Origin of Species by Means of Natural Selection.
Skelton, P. 1993. Evolution: A Biological and Palaeontological Approach. Prentice Hall, 997 pp.
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