After millions of years of evolution, human males will adapt to become nothing more than a cock and balls. At this point the male's sole purpose would be to be used as a dildo a female. The penis would be fully developed when it comes out of the womb. Much like moths, males would have a large store of fat so they could last months without eating. They would have a tiny hole on the top to act as a breathing tube. No mouth, eyes, body, or brain would be needed.