Charles Darwin’s theory of evolution by natural selection, published in 1859, explains that 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 random 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 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 and 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.