What Did Darwin Say About Mutations?

Charles Darwin’s famous book, On the Origin of Species, was first published in 1859. What did he say in his book about mutations? Nothing! This is not a criticism of Darwin, it’s just that mutations had not yet been discovered. For the same reason, Darwin did not know about DNA, genes, and the like. But one thing he did know, and what was obvious to anyone, was that offspring of animals exhibited variations. He also knew that people had long been able to cause these variations to accumulate by using selective breeding, which he called “artificial selection.”1 Like other people, Darwin believed that dog breeds as diverse as Great Danes and Chihuahuas had been developed centuries earlier by selective breeding.2 But no one at that time, including Darwin, knew why variations occurred in offspring. Darwin freely admitted this in his book:

I have hitherto sometimes spoken as if the variations…had been due to chance.  This, of course, is a wholly incorrect expression, but it serves to acknowledge plainly our ignorance of the cause of each particular variation.” 3

Even though Darwin admitted that he did not know what caused variations to occur, he assumed there was no limit to them. Then he used that assumption to infer that with unlimited time selection could accumulate enough variations to cause unlimited change. Here is how Darwin explained it in his book:

“Slow though the process of selection may be, if feeble man can do [so] much by his powers of artificial selection, I can see no limit to the amount of change…. which may be effected in the long course of time by nature’s power of selection.” 4

Darwin was aware that not everyone made the assumption that variations were unlimited. He even pointed out that others were making the opposite assumption:

“It has often been asserted, but the assertion is quite incapable of proof, that the amount of variation under nature is a strictly limited quantity.”5

But Darwin’s assumption of unlimited variations allowed him to conclude that a species could eventually change into a totally different species. It even allowed him to infer that one primordial species changed into all other species on earth:

“Therefore I should infer from analogy that probably all the organic beings which have ever lived on this earth have descended from some one primordial form” 5

Keep in mind that all of this stemmed from Darwin’s initial assumption that there was no limit to the amount or type of variations even though he admittedly did not know what caused variations to occur.

But today we know of two sources of variations:

a) “Shuffling” of gene alleles.6 Shuffling results in different combinations of existing alleles. Although the shuffling of alleles creates variations, such variations are limited in number since there is a limited number of ways for the alleles to be shuffled (somewhat analogous to the limited number of ways a deck of cards can be shuffled).

b) Mutations. Mutations are copy mistakes that occur when DNA is duplicated, but such copy mistakes have never been known to increase the complexity of DNA. This should come as no surprise since copy mistakes are never expected to make a complex writing more complex. So, although typos certainly occur in DNA there is no evidence that they can help create the complex information required to change an organism into a different type of plant or animal. (See Chapter 7: Where did my DNA Come From? and Chapter 8: Limitations of Mutations ).

People have always been able to develop very diverse breeds of dogs by using selection to accumulate variations caused by (a) and (b) above. But neither (a) nor (b) has been shown to provide the type of variations needed for the numerous innovations required to change bacteria into trees, birds, and people.

It is important to realize that selection is not a source of variations. Selection only causes a variation to become more common or less common in a population. Selection has nothing to do with a variation occurring in the first place.

References and Notes for Chapter 10:

1. It is widely believed that Darwin originally coined the term “artificial selection” as another name for selective breeding.

2. I explain this in more detail in Chapter 4: What Natural Selection Can and Cannot Do.

3. Charles Darwin, On the Origin of Species, First Edition, 1859, Chapter 5.

4. Charles Darwin, On the Origin of Species, First Edition, 1859, Chapter 4.

5. Charles Darwin, On the Origin of Species, First Edition, 1859, Chapter 14.

6. Alleles are alternate forms of a gene. (See Chapter 4: What Natural Selection Can and Cannot Do )