[Federalist] Americans are having fewer babies. In 2018, age-controlled fertility may fall to near the lowest level in our history. We aren’t alone in this: fertility rates have fallen across much of the western world, despite widespread economic expansion.
The main reasons for this are sociological: declining marriage, rising cost of childbearing, and related factors that amount to cultural norms and practices.
Recently, scientists have raised a different alarm bell: human biology may be changing. For decades, some scientists have been arguing that men are producing less sperm than they used to, but these studies were plagued by small sample size, non-randomly selected men, or other methodological problems.
Last summer, however, a research team in Israel (the country at the forefront of reproductive technology) assembled a massive dataset, combining hundreds of prior studies, creating a sample of tens of thousands of men across decades. They found that male sperm counts are indeed in decline.
While their findings aren’t universally accepted, they have succeeded in persuading a large number of former skeptics. The sample sizes are sufficiently large, the extra checks for possible counterarguments sufficiently robust, and the findings sufficiently clear in the data that it’s time to take seriously that men really may be losing some degree of their biological fertility. |