When it comes to fertility, the only part of a man's nether region that matters is the part nobody ever bothered to measure: the taint. Scientists at the University of Rochester Medical Center have found that the "anogenital distance"—the distance between a man's scrotum and anus—correlates with male fertility. The greater the grundle, the higher the sperm count. If a man's balls and asshole are less than two inches apart, he is 7x more likely to be "sub-fertile" than his large-grundled peers.
Male private part size anxiety: More complicated by the day.