London: Apart from genes, environment and lifestyle factors that lead to chemical modifications of human genes can also influence a child's pubertal timing, a new study has found. Chemical modifications of the human genome -- epigenetic modifications -- occur when girls and boys enter puberty. The findings showed that epigenetic changes cause the unregulation of genes that are important for pubertal development. Further, highly specific changes in a child's DNA methylation -- a process by which methyl groups are added to DNA-- could differentiate children according to whether they had entered puberty or not and thus may be used to predict a child's pubertal stage. "Changes in the DNA methylation patterns can be caused by many different factors. However, we could see very specific changes when children went through puberty, and have subsequently shown that this also leads to changes in the expression of the methylated genes," said lead researcher Kristian Almstrup from Rigshospitalet in Copenhagen. Due to the changes in the epigenetic control of the gene, the "puberty genes" TRIP6 -- Thyroid Hormone Receptor Interactor 6, has been found to increasingly express through puberty. Epigenetics is a leading mechanism by which our environment communicates with our genes and as a result also controls whether, where and to what extent the genes are expressed. The identified epigenetic changes during puberty are therefore our best lead towards understanding how environmental factors can affect pubertal onset, said the paper published in the journal Scientific Reports. "The study demonstrates how the environment can affect the pubertal onset in humans. It gives us a significant insight in to the crucial role of epigenetic factors on our reproductive development," added Anders Juul, Professor at Rigshospitalet in Copenhagen. For the study, the team focused on the role of epigenetics in teenage girls and boys. They found a number of areas in the human genome, which is controlled epigenetically during puberty. In girls' the pubertal onset was observed to decrease from 11 to 10 years. Boys too showed similar, but less pronounced, changes.