In South America, Darwin found fossils that resembled modern animals however, they had differences in size and adaptations. It made him realize living things had ancestors and that species changed over time. This idea was radical as most people believed that life on Earth remained the same throughout history. Darwin found many varieties of finches on the Galapagos Islands which are 600 miles from South America, the nearest land mass. He reasoned that the ancestral birds must have come from there in the past and somehow changed over time into the various finch species he encountered. He realized that not only did species change over time from discovering many fossils in South America, he also noted that the Earth itself changed over time geologically--land masses can rise and fall, and new land can form. Darwin learned that tortoises in the Galapagos were slightly different in terms of their shells from island to island and different still from those in South America.
FIrstly, he discovered that the population was exceeding the capacity that the island can support.
therefore individuals that is more adapted to the enviornment will survive while those are less competitive will die
Eventually the more adapted indivuals will reproduce and therefore passing the favourable trait to their offsprings.
The diffrent shapes of bird beaks were because adaptation to their diets. and the tortise shells were shaped and structured differently.mice were spotted for camoflague.