In the Galapagos Islands he observed that tortoise populations from each island were subtly different. Darwin also worked with finches and found that although they were much like finches on the mainland, their beaks were modified. Like other scientists, Darwin's ideas were influenced by his readings. Among the work he attributed to the formulation of his theory was a paper by Malthus, a mathematical biologist. This is a concept we will explore in some detail in future chapters.
Organisms can produce more progeny than can survive.
Darwin used the example of elephant populations growing from just 2 to over 19,000 in short time. Environment dictates fitness. Natural selection results in new species. Traits accumulate and transform organisms. Evidence to Support Darwin's Theory is abundant.