One of the easiest ways to understand Darwin’s conclusions is to look at his studies of finches on the Galapagos Islands. These islands are over a thousand kilometres from the nearest land mass and the finches found on the islands all have small differences in size and types of beak. Darwin’s studies led him to the conclusion that the birds on different islands had changed, evolved, to be best suited to the environment on the island. Their beaks may be the best way to explain Darwin’s discovery. Thin, sharp beaks prevailed where the main food source was insects and grubs; large claw-shaped beaks prevailed where the diet was predominantly buds fruit and nut.
While these findings were key to Darwin’s conclusions, it was much later that he drew his conclusions. Many textbooks are confused about this but credit would still be given to candidates who follow this line.
Darwin proposed that these differences had come about over a long period, a period where survival traits were passed on from the most suited parents to their offspring until the only kind of finch on each island was one that fitted that environment. Hence he came up with the phrase ‘survival of the fittest’. This theory also explains how some species die out when the environment no longer suits them; it also explains why some seeming mutations in species lead to an improvement in their survival while others are an evolutionary dead-end. Ultimately this process will bring about new species. As a theory it not only explains the variety of species but predicts the need for continual changes both positive and negative among species.
This theory, for Darwin, made sense not only of his findings from the 5-year voyage but of his questions about man’s place in nature; though he did not publish these finding for a very long time due to his realisation that the theory would undermine much of what most scholars and religious believers thought about themselves.