Past Years

In past years the goal of geneticist was to determine whether or not intelligence was heritable. Most studies in past years where conducted on monozygotic twins (meaning coming from one egg) and dizygotic (coming from separate eggs). The reason these test where conducted on twins is because monozygotic twins DNA are more identical than that of a clones. Therefore there would be little variants in their DNA strands making it easier to identify very minute differences. The test of the past conducted on twins showed that general intelligence was very heritable. In fact the result showed that as much as 40% in children and 80% in adults was inherited according to studies conducted by Danielle Posthuma and Eco. De Geus(151). Other studies done in the past showed that other factors influenced the level of general intelligence things such as protein level and brain size.