NCBI ROFL: An explanation for the shape of the human penis.

"The present form of the human penis, reached over several million years of evolution, was orchestrated by the vagina of the human female. The multifunctional vagina serves as a birth canal, a component of the structural support for the internal pelvic organs, and as a coital organ. In this last function, it has had an evolutionary effect in shaping male sexual anatomy. Hominid fossils so far discovered show that the female pelvis evolved to accommodate the increasing size of the brain of the human infant. Larger cranial capacity necessitated a larger birth canal and, as a result of sexual selection, an increase in the size of the penis. Compared to that of the other great apes, the human penis is considerably larger, and evidence suggests that its unique configuration may also be a result of vaginal influence. It has been proposed that the shape of the glans with its distinctive ...