Miscellaneous articles

The theory of evolution by natural selection in one sentence

Darwin’s beautiful idea

Black and white photo of Charles Darwin.

Charles Darwin (1809–1882)

Charles Darwin’s theory of evolution by natural selection, published in 1859, explains how all of life on Earth today evolved over the eons from less complex forms. And the essence of this grand theory can be captured in a single sentence:

Within a species there’s always slight random variation in the hereditary traits of its members, and those variations that happen to be the most conducive to survival and reproduction will naturally tend to become widespread in the species.

The process of evolution by natural selection therefore involves the non-random ‘selection’ by nature of particular variations, which become established in the species. And the steady accumulation of innumerable such small changes over hundreds of millions of years has led to the extraordinary complexity and diversity of today’s plants and animals.

The ever-present slight random variation in hereditary traits within a species – the fuel of evolution by natural selection – is ultimately due to the continuous occurrence of random gene mutations, which have several causes, including gene copying errors during reproduction.

This beautifully simple theory, so often misunderstood or misrepresented, explains how the appearance of design in plants and animals arose from a mindless process. Evolution by natural selection is as natural and inevitable as water flowing downhill.

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This article was inspired by the book The Moral Animal by Robert Wright, which presents in chapter 1 the theory of evolution by natural selection in a single sentence. My attempt to present the theory in a sentence was based on Wright’s.

The point that evolution by natural selection is as natural and inevitable as water flowing downhill came from the book The Adapted Mind by Leda Cosmides and John Tooby.

My understanding of the theory of evolution by natural selection comes mainly from the books The Selfish Gene and The Blind Watchmaker, both by Richard Dawkins.


The content of this article can change, and so referencing of it should state the date of reading. Also, you can save the current version in the Internet Archive and then link to the archived copy.

The article was first published in 2016.