“I think you can tell it’s for a lay audience,” says Michael Carroll, holding up his book, Your Nuts, its cover illustrated with two walnuts in a string bag. The book has arrived in tandem with worldwide concerns about falling birth rates. “Spermaggedon” is a chunky piece of this puzzle, part of a wider debate about whether and why we’re heading for species-icide. Are people deciding not to have kids because of climate anxiety and economic precarity? Or is this an unchosen fertility cliff edge, created by forever chemicals and our lifestyles? This is not a drill, says Carroll, a biologist and reproductive scientist at Manchester Metropolitan University. “There’s compelling evidence to support a historical decline in sperm count and sperm concentration over the last number of decades.” However, it’s just not that simple.
First, it’s not a uniform picture and in some populations sperm counts are going up. The Danish Young Men Study, for instance, showed no drop between 1996 and 2022. In Ireland, a study of 15,000 men between 2008 and 2023 showed a 23% increase in sperm concentration.
