Some molecules found in foods are known to be capable of driving DNA methylation or DNA demethylation. For example, folic acid (a vitamin), vitamin B12, and choline are thought to increase methylation. Based on this consideration, why would it be important to avoid eating excessive quantities of such molecules (while being certain to eat sufficient quantities for health)

Eating excessive quantities of such molecules could deregulate this process, increasing methylation and repressing the expression of genes that should normally be expressed.

Explanation:

DNA methylation is one of the epigenetic mechanisms involved in the regulation of gene expression, because it is a process by which methyl groups are added to DNA.

Methylation then modifies the function of DNA when it is found in the promoter gene, it is essential for normal development and is associated with a number of key processes, including genomic imprinting, inactivation of the X chromosome, repression of repeating elements, aging, and carcinogenesis. Usually, it acts to suppress gene transcription.

For example, folic acid is essential for the rapid cell division that occurs during early fetal development and it also plays an important role in methylation and thus in gene regulation. The metabolism of these vitamins is aimed at achieving adequate levels of  DNA methylation, necessary for the cellular processes. Eating excessive quantities of such molecules could deregulate this process, increasing methylation and repressing the expression of genes that should normally be expressed.

a time line cause it goes from 685 to 978

the answer is:

carbon dioxide