Human evolution

Primate Evolution

The theory of evolution began when man first noted his distinct similarity to apes . The possibility of a common ancester with the modern apes had been discussed since the mid 1800 's , but it wasn 't until Charles Darwin published his book , On the Origin of Species in 1859 that the idea was considered legitimate . Since that time , fossil records have helped us to deliniate and define our evolutionary history and to describe the many human-like species that have lived on the earth over the last 8 million years p

Charles Darwin studied a population of finches that had been isolated on the Galapogos Islands , and described the theory of natural selection whereby over time , each finch had changed in ways that made it more successful in a particular niche . He observed fourteen different species of finches , all who were very similar , except for the size and shapes of their beaks . He noted how each type of beak was shaped very specifically for the type of food the bird ate and explained that the changes were due to the natural selection of the characteristics in a species that made it more successful at obtaining food and at reproducing . If a finch with a slightly longer beak was more efficient at eating termites from holes in trees , he would survive longer and reproduce more than his short beaked counterparts who ate termites . His offspring that inherited his slightly longer beak would also survive longer and reproduce more Over time , the longer beaked finches would be more prolific than the shorter beaked version within that particular niche and the adaptation would flourish while the shorter beaked finches would die out Eventually , speciation occured (the development into reproductively separate species , as the termite eaters with longer beaks became more distinctly separate within their environment and became reproductively isolated . This gradual change of a segment of a population into reproductively different species , in response to an environmental pressure (competition ) for survival factors is called adaptive radiation

Although Darwin mentioned nothing about human evolution in his first book , his science minded peers were able to understand how his theory applied to humans . Initially there was much debate by the general population over the idea that humans could have evolved from the same lineage as an ape , but by 1870s , the scientific community had already come to the general conclusion that a fossil record would be found in Africa , where our great ape relatives were found . In the 1920 's , as predicted , Raymond Dart found bones from Australopithecus africanus , a hominid who lived between 2-3 million years ago in the Pliocene Era They were discovered in a cave in Africa . From the skeletal structure he was able to determine that the specimen was bipedal a defining trait of humans , and the size of its braincase was between that of modern humans and apes . Since that time , paleoanthropologists have been able to trace the evolutionary history of the primates including hominids , for some 85 million years...