Identical twins grow apart, genetically, as the years pass, a team of European and US researchers reported on Tuesday (July 5). Their study of identical twins show the genetic code itself does not change, but rather chemical changes after birth alter the way the gene is expressed, a process known as epigenetics.
"Most importantly, we found a direct association between the remarkable epigenetic differences observed and the age of the monozygotic (identical) twins: the youngest pairs were epigenetically similar, whereas the oldest pairs were clearly distinct".