Genealogists study the lives of humans throughout the ages. It appears that future genealogists will have it easier to make such studies due to a dwindling number of humans.
Five years ago, a study describing a precipitous decline in sperm counts sparked extreme concerns that humanity was on the path to extinction. Now a new study shows that sperm counts have fallen further and the rate of decline is speeding up, raising fears of a looming global fertility crisis. From a report:
The initial study, published in July 2017, revealed that sperm counts — the number of sperm in a single ejaculate — plummeted by more than 50 percent among men in North America, Europe, Australia, and New Zealand between 1973 and 2011. Since then, a team led by the same researchers has explored what has happened in the last 10 years. In a new meta-analysis, which appeared in the journal Human Reproduction Update, researchers analyzed studies of semen samples published between 2014 and 2019 and added this to their previous data. The newer studies have a more global perspective and involved semen samples from 14,233 men, including some from South and Central America, Africa, and Asia. The upshot: Not only has the decline in total sperm counts continued — reaching a drop of 62 percent — but the decline per year has doubled since 2000. The 2017 report also revealed that sperm concentration (the number of sperm per milliliter of semen) dropped by an average of 1.6 percent per year, totaling more than a 52 percent among men in these regions over the previous four decades.