Secrets of the Phallus. I'll paraphrase, but a basic understanding of evolution is necessary. The adaptiveness of a long penis was obvious - you can go deeper and ejaculate closer to the cervix, increasing chances of fertilisation (babies!). More interestingly, another seperate idea is that mushroom-shaped heads (heads where the "coronal ridge", the distance from the base of the glans to the top of the shaft) are more likely to result in fertilisation because they pull other men's semen out of your lover's vagina. That's right. Next time you're bragging about your bulbous glans, remember that nature gave you that to scoop out other men's jizz. Sigs should now include length, girth, and distance from the tip of the glans to the shaft.