Human Evolution Essay From 55 million years to present day, there has been development from the earliest primates to modern day human beings. This progression starts with apes, to australopithecines, the intermediate, to humans. Fossil discoveries of protohominins have been made, and are divided into three genera: Sahelanthropus, which dates back to 7 to 6 million years ago, Orrorin, which existed 6 million years ago, and Ardipithecus, with fossils from 5.8 to 4.4 million years ago. The first australopithecines had not begun to evolve until approximately 5 million years ago, and were decidedly living by 4.2 million years ago. At 3 million years ago, australopithecines then became more common in more places, such as North Central, East, and South Africa, meaning they were able to adapt to more environments and conditions. They continued to generate two lines of hominins 2.5 million years ago; one that would evolve into the early humans, and another that would go extinct 1 million years before them (O’Neil, https://www2.palomar.edu/anthro/hominid/australo_1.htm). Multiple discoveries of intermediate fossil evidence has helped support the existence of hominins and the evolution through australopithecines and homo genus. An anatomy professor, Raymond Dart, had found a fossilized skull in 1924. This small skull, Australopithecus africanus, had its foramen magnum nearly centralized, and also had short teeth, meaning that it resembled a human more than an ape. Following this, Robert Broom, a medical doctor and paleontologist, founded more fossils belonging to africanus and early hominins in 1938. These earlier hominins, named Paranthropus robustus, had sagittal crests and large jaw muscles, being more similiar to an ape than human (O’Neil, https://www2.palomar.edu/anthro/hominid/australo_1.htm). Overall, there are 12 species of early hominins that were founded, and existed between 6 to 1.5 million years ago (includes both the Australopithecus africanus and Paranthropus robustus). The two discoveries and twelve intermediate species show the progression through the australopithecine and homo genus, and prove that homonins existed and derived from the homo genus (O’Neil, https://www2.palomar.edu/anthro/hominid/australo_2.htm). Environmental stress was a major cause of evolution, and forced species to change and adapt. An environmental stress is seen during the Pleistocene epoch, where there were severe climate swings. This had affected the human evolution; while animal species had died, humans instead became more flexible with the weather and intelligent. Along with the animal species that lived, during the ice ages of the Pleistocene epoch, humans developed larger bodies to maintain and generate more heat (O’Neil, https://www2.palomar.edu/anthro/homo/homo_3.htm). Another weather stress human evolution faced during the Pleistocene epoch was the heat of East Africa. To avoid overheating, their bodies adapted to the warmth and the species had become hairless, which gave them an advantage during hunting, for other mammals were not able to cool themselves as easily while running (O’Neil, https://www2.palomar.edu/anthro/homo/homo_2.htm). In addition, the environment itself was another environmental stress that humanity had to adapt to. Around 3 million years ago, during the Pliocene epoch, early hominins had developed shorter length and rounder pelvises for bipedal locomotion, or walking on two legs. This would be due to the grass and woodland environments, and the benefits it had, with being able to view over tall grasses and to see more in general. When this happened, though, their legs had grown and become stronger, and their arms were used more to hold and carry objects instead (O’Neil, https://www2.palomar.edu/anthro/hominid/australo_2.htm). Because of these environmental stresses, the human species was forced to react and adapt, changing their lifestyles. I believe in human evolution, and that humans do derive from apes. With the given evidence of the homologous structures and intermediate fossils, and relative dating, I think that the claims scientists make about evolution are true and valid. From the comparison of the skulls and pelvises to bipedalism, I think that evolution cannot be denied, and it proves the progression of apes, to australopithecines, to humans. Overall, my stance is that evolution is how humanity came to be.