The world’s average penis length has grown a staggering 24 percent, on average, over the past three decades, a new meta-analysis of 75 previously conducted studies found. Dr. Michael Eisenberg, a professor of urology at Stanford Medicine, compiled a dataset which measured the average erect penis length of 55,761 men, taken between 1942 and 2021. His findings, aptly published on Valentine’s day in the The World Journal of Men’s Health, showed a large increase in recent years which he says may be cause for concern rather than celebration. “The increase happened over a relatively short period of time,” Dr. Eisenberg told Stanford Medicine’s Scope blog. “Any overall change in development is concerning, because our reproductive system is one of the most important pieces of human biology. If we’re seeing this fast of a change, it means that something powerful is happening to our bodies.” It’s unclear what, exactly, has caused the change—though Eisenberg points to chemical exposure, junk food, and sedentary lifestyles as some potential culprits.