At some point between apes and Ardipithecus, a mutation must have occurred that allowed bipedalism to become a reproductive advantage (Kottak, 2015). Gene flow is the exchange of genes between populations (Wilreker, 2016). Gene flow and interbreeding allowed the favorable trait of bipedalism to spread and multiply. Genetic drift is the change in gene frequencies as a consequence of random variation rather than natural selection (Wilreker, 2016). Individuals within the population without the favorable bipedalism trait would begin to die and not reproduce. As the population grew, members no longer carried the Quadrupedalism trait. Natural selection its the elimination of unfit individuals and the genes they carry (Wilreker, 2016). Since bipedalism was a favorable trait, eventually those with Quadrupedalism would no longer be chosen to reproduce …show more content…
However, they didn’t quite move like we do. The Ardipithecus pelvis appears to be transitional between being suited for climbing in trees and being modified for walking on two legs (Kottak, 2015). A fairly complete skeleton of Ardipithecus ramidus, named “Ardi” is the earliest known hominin Australopithecus afarensis lived around 3 million years ago (Kottak, 2015). Fossils, including the well know skeleton named “Lucy”, show that they had a mixture of apelike and hominin characteristics (Kottak, 2015). The lower spine, hip joint, pelvis, and thigh bone changed in accordance with the stresses of bipedal movement (Kottak, 2015). The blades of the australopithecine pelvis are broader and shorter than those of the ape (Kottak,