Anyone care to disagree with my answer to this question, posed by the esteemed Moderator of The Visualiser.net - Compare your cock!..?? "I think that men have a head for the same reason that they have nipples. In developmental terms, the glans derives from the clitoris, and they are functionally similar in that they serve as foci for nerves that are important in copulation -- in women, to facilitate reception/penetration of the penis; in men, to trigger ejaculation during penetration. In other words, the head's at the end of the shaft because that's the part that goes in the girl because that's were you need to nut in order to make babies! Ejaculative force and sperm mobility make length in this regard insignificant. It is interesting to note, however, that human penis size is proportionally larger -- by a lot -- than any other primate. I think this, too, has very little to do with evolutionary fitness models.. ...to summarize: 1) Men need to ejaculate for fertilization to be successful 2) Fertilization is most successful from vaginal penetration 3) Nerve stimulation triggers ejaculation Consequently, nerves are concentrated in the area most likely to penetrate the vagina: the tip. Ergo, the glans. The specific shape of the glans also favors penetrative sex -- nerves are concentrated along the basal edge of the glans, which "flares" outwards, promoting sensitivity to "reverse thrusts" -- ie the "pulling out" motion -- which facilitates constant/repeated penetration, again which facilitates successful fertilization. The specific location of the penis (and therefore glans) is partially constrained by our evolutionary history and embrionic development as essentially "female.""