primates are more cognitively advanced than other mammals and that the degree of cognitive awareness and ability grows significantly from prosimians to humans. However, researchers still debate which parameters should be used to define and compare intelligence as well as the causal factors leading to this cognitive growth. Intelligence is a concept hard to define and even more difficult to test for in living species. In studying how human intelligence evolved, scientists are faced with a dilemma; how to determine the intelligence of individuals that no longer exist?

Methods that have been used to determine the level of intelligence in animal ancestors include the comparisons of the volume of the braincase, brain size to body weight and neocortex development. Studying social behavior also gives clues to cognitive level. Anthropologists, for example, have a variety of theories on what caused the significant leap in intelligence from the prosimians to humans. Which...
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