Further evidence has been found which shows that the environment and life experiences, and not only DNA, can contribute to the development of the human personality. In other words, genetics doesn’t account for everything. This was shown by a paper published in Science (340; 756-759, 2013), in which a group of German researchers showed that after subjecting 40 genetically identical mice to different external conditions during a three-month period, they found differences in the way the mice develop, which shows that personality of an adult isn’t entirely determined by their genetic constitution.
This same phenomenon was also observed in a very interesting article published in Genome Research on 3 June. Here, the methylation of DNA was studied for the first time on twins at birth – an important study given that DNA methylation can affect their development. The authors emphasise the influence of the intrauterine environment on epigenetic change in newborns.
Both articles underscore the role played by epigenetic mechanisms in the development of an individual’s personality.
Epigenetic mechanisms are those which affect the genome when it interacts with the environment, but which do not affect the nucleotide structure of the DNA. Most are attributable to DNA methylation in some nucleotides. In everyday language, one can say that epigenetics is all that which can affect human development that isn’t attributable to its genome.
Two people may be genetically identical with identical genomes, but may develop differently due to the influence of the environment, which changes the expression of their genes, and as a result, leads to the individuals with differing phenotypes (their adult personality).