For the ancient Greeks, the human body was perfect. Explore this example of the mathematical source of ideal beauty.
Roman copies of ancient Greek art
Basically, just about every Roman wanted ancient Greek art. For the Romans, Greek culture symbolized a desirable way of life—of leisure, the arts, luxury and learning.
The popularity of ancient Greek art for the Romans
Greek art became the rage when Roman generals began conquering Greek cities (beginning in 211 B.C.E.), and returned triumphantly to Rome not with the usual booty of gold and silver coins, but with works of art. This work so impressed the Roman elite that studios were set up to meet the growing demand for copies destined for the villas of wealthy Romans. The Doryphoros was one of the most sought after, and most copied, Greek sculptures.
Bronze versus marble
For the most part, the Greeks created their free-standing sculpture in bronze, but because bronze is valuable and can be melted down and reused, sculpture was often recast into weapons. This is why so few ancient Greek bronze originals survive, and why we often have to look at ancient Roman copies in marble (of varying quality) to try to understand what the Greeks achieved.
Why sculptures are often incomplete or reconstructed
To make matter worse, Roman marble sculptures were buried for centuries, and very often we recover only fragments of a sculpture that have to be reassembled. This is the reason you will often see that sculptures in museums include an arm or hand that are modern recreations, or that ancient sculptures are simply displayed incomplete.
The Doryphoros (Spear-Bearer) in the Naples museum (image above) is a Roman copy of a lost Greek original that we think was found, largely intact, in the provincial Roman city of Pompeii. 
The idea of a canon, a rule for a standard of beauty developed for artists to follow, was not new to the ancient Greeks. The ancient Egyptians also developed a canon. Centuries later, during the Renaissance, Leonardo da Vinci investigated the ideal proportions of the human body with his Vitruvian Man .
Polykleitos’s idea of relating beauty to ratio was later summarized by Galen, writing in the second century,
Beauty consists in the proportions, not of the elements, but of the parts, that is to say, of finger to finger, and of all fingers to the palm and the wrist, and of these to the forearm, and of the forearm to the upper arm, and of all the other parts to each other. Galen, De Placitis Hippocratis et Platonis
 Recent scholarship suggests that the Doryphoros sculpture in the Naples museum may not have been found in a Palestra at Pompeii. See Warren G. Moon, editor, Polykleitos, The Doryphoros and Tradition (Madison: University of Wisconsin Press, 1995).
Smarthistory images for teaching and learning:
[flickr_tags user_id=”82032880@N00″ tags=”doryphoros,”]