The question was bound to come up sooner rather than later. Given the anxiety so many young women today have about whether to freeze their eggs, it's only reasonable to wonder whether men should be worrying too.
In the United Kingdom, for example, the average age of fathers has gone from 31 in the 1990s to 33 now. "It's time we took seriously the issue of paternal age and its effect on the next generation of children," he told the BBC.
(In the United States, census bureau numbers show the average age of fatherhood rose from 25.3 in 1987/88 to 27.4 in 2006/2010. See chart below.)
Over the past 24 hours Smith's commentary has triggered strong reaction -- ranging from soul-searching to derision -- from those taking the time to ponder the issue. In the British press, Allan Pacey, a University of Sheffield professor who focuses on male health, decried the idea as "one of the most ridiculous suggestions I have heard in a long time" and "simply crackers."
The British Fertility Study took issue with the suggestion that sperm banking could provide men with the security they might be looking for, pointing out that frozen sperm tended to be less fertile and suggested that governments could deal with the issue by focusing on how to better support young couples who decide to have children.
Smith's concerns are not unfounded, however.
In recent years a number of studies have found links between delayed fatherhood and a risk of autism, schizophrenia and other conditions in their sons and daughters. Some researchers even claimed to show that older fathers appear to have less attractive children.
One key study in the field was published in 2012 in the journal Nature and showed that the father's age at conception was the dominant factor in mutations in children.
Kari Stefansson, a researcher in Reykjavik, Iceland, explained in a report in LiveScience at the time that "a 36-year-old father gives twice more new mutations to his child than a 20-year-old father does, and a 50-year-old father gives about four times the number of mutations. This is not a subtle effect — this is a very, very large effect. And it increases the probability that a mutation may strike a gene that is very important, which can lead to a disease."
While these studies do not provide any "cut-off" age over which a man would be putting his offspring at an unreasonable risk, the most dramatic effects appear to be in children born to fathers age 45 or older. So if you're older than 18 and concerned, there's still probably plenty of time to freeze those sperms.