A new study gives a lot more weight to the father when it comes to passing down genetic disorders to children. A team called Decode Genetics studied the effects that the father's age has on children, and whether or not older dads had a statistically significant impact on passing down genetic mutations.
In fact, it found that 97% of all mutations passed to children come from older fathers.
How old are we talking? The results from the study found that a child from a 20-year-old father inherits an average of 25 mutations, while the child of a 40-year-old father is likely to get more like 65 mutations.
"Society has been very focused on the age of the mother. But apart from [Down's Syndrome] it seems that disorders such as schizophrenia and autism are influenced by the age of the father and not the mother," said lead researcher Dr. Kari Stefansson.
The difference is that males continue to create new sperm throughout their lives, and as with every other part of the body, as they get older there is a greater chance for problems to arise. Women, on the other hand, are born with all their eggs so age is not as much of a factor.
The study, published in the journal Nature, did not say that older men should stop having children. Although the risk of passing on significant mutations is more than doubled for men over 40, that risk is still very small.