Theory of natural selection states that some of the species get suited in a particular environment more in comparison to others and hence some species survive for a longer duration than others. They also adapt according to the surrounding. Darwin was attracted towards different types of finches seen in the Galapagos. The class of all the birds were similar but at different islands the size and shape of the beaks were different. Darwin discovered that this was mainly due to the availability of different type of food. The beaks of the birds got adapted to have different types of food. Hence the natural selection theory worked perfectly in the case of finches in the Galapagos Islands. Similarly, this theory applied well on Australopithecines who were part of hominid species found in Africa. The main characteristic of this class was that they were bipedal and the size of brain was too small (Haviland, 2013, 35-60). So the bipedalism was something which was a very unique feature of humans which evolved on the demand of adaptation.