Here’s a plain example about dna.
Summary: Researchers have mapped the relationship between length of pregnancy and chemical DNA changes in more than 6,000 newborn babies. For each week’s longer pregnancy, DNA methylation changes in thousands of genes were detected in the umbilical cord blood.
Like anything in the world it’s not black and white.
There are many intricacies that people aren’t taking into account.
Something to think about atleast 
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