First, if we're going to take an in depth look at the penis, the one-eyed trouser snake, the pocket python, the skin bus fresh from tuna town, then we should start by observing the artistic importance of the phallus through the centuries.
"...the artistic evidence implies that over-large genitals were considered aesthetically unpleasing by the Greeks and Romans....the ideal type of male beauty epitomised in classical sculpture, Greek and Roman, normally depicts genitals of somewhat less than average size...certainly never more. Consequently, the exaggerated genitals of Priapus (right) made him seem an ugly and grotesque figure, though benevolent.
It has also been pointed out that many of these images are of athletes, and during and immediately after hard exercise (and not only in cold water) the penis is considerably shrunk and the testicles hoist high. *cough* steroids! This also affords a commonsense explanation for the apparently phimosed appearance of the foreskins in classical statuary and vase painting.
Somehow I get the feeling by the end of the week I'll have seen more cock than Tracy Lords.
We should never assume that the Greeks, Romans and Etruscans considered images of penises as we do. They used them on amulets to ward off the evil eye, -a lot of good that did the poor guy in the car from Sunday's post- with no more thought for sexuality than we consider crossed fingers to be a Christian symbol.
So the small penises shown on ordinary mortals may have been no more than a convention, to distinguish them from fertility figures such as satyrs and Priapus - which were much more significant in an age when the fertility of plants, beasts and people could not be taken for granted or brought under human control by material means.