Fifty years ago, there were no sperm banks.
There were no over-the-counter fertility tests, no proprietary zinc supplements for virility, and men pretty much took for granted that when the time came, their "swimmers" would do their job.
Fast forward five decades, and the average man in his 20s and 30s lives in a state that might be aptly described as sperm count paranoia.
"There has been scientific evidence that sperm counts have been dropping worldwide over the past 50 years," said Cynthia Daniels, associate professor of political science at Rutgers University and author of "Exposing Men: the Science and Politics of Male Reproduction."
"This evidence has been met with two extremes—either profound skepticism or a reaction that verges on public panic."
Thus far, solid scientific proof to completely back these fears has been elusive. But to paraphrase an old saying, just because you're paranoid doesn't mean environmental factors aren't killing off your sperm.
Some research studies do suggest that male sperm counts are falling across the globe, and a number of scientists are working to determine the real-world influences that might be causing a reduction in "swimmers."
Many researchers report there are a number of fertility-damaging culprits that may lurk within our workplaces, reside in the heat at the bottom of our laptops, float in our drinking glasses -- and possibly even rest on the dinner plates of mothers pregnant with male children.
"I think the evidence is growing that chemicals in the environment do affect a man's sperm count," said Shanna Swan, director of the Center for Reproductive Epidemiology at the University of Rochester School of Medicine. "It's probably not universal, but it is pretty good evidence for a decline in Western countries."
Daniels said these findings have been met with equal measures of fear and defensiveness, as they strike at the heart of social norms regarding masculinity.
"Others strongly contest these findings and say that the evidence is the result of social hysteria -- just one more example of men (and manliness) under attack in the 21st century," she added. "One thing is clear -- this question is socially and politically loaded because it involves not just questions of male health, but of how we view men in the world today."
Twenty million of anything may seem like quite a bit to most people. But if it's a milliliter of semen you're talking about, this number of sperm just barely cuts it.
"Semen typically contains 70 million sperm per milliliter," Swan said. "That's a lot. But if you get to the low end of the concentration spectrum -- anywhere below 20 million sperm per milliliter -- your fertility could be affected."
The simple reason for this, Swan explained, is because you need a lot of sperm in order to have a reasonable chance of one making it to the egg of your partner, as the odds of any one sperm actually fertilizing an egg are infinitesimal.
"In a lot of studies, if the count falls below 40 million, a man's chance of conception in a given month is decreased," Swan said.