BC), Shang dynasty China (1600–1050 BC), Minoan Crete (2700–1450 BC), Classical Greece (550–323 BC), and ancient Rome (510 BC–476 AD). With this "ancient harness", ploughs and carts were pulled using harnesses that had flat straps across the neck and chest of the animal, with the load attached at the top of the collar, above the neck, in a manner similar to a yoke. These straps pressed against the horse's sterno-cephalicus muscle and trachea which restricted its breathing and reducing the pulling power of the horse. Thus, the harder a horse pulled, the more strongly it choked off its own breathing. Because of these supposed physical constraints, oxen were used in preference to horses for heavy work, as they do not have this problem due to anatomical differences and could be yoked to their loads. In 1972, Spruytte published Ancient Harness Systems which argued that there were at least three ancient traction systems shown in art, none of which choked the horses. The shoulder traction (ancient Egyptian) and breast traction (Greek and Roman) artwork had been mis-seen and mis-drawn as a composite that matched neither. This he sought to demonstrate by building reproduction chariots and harness, and running them with suitable teams. These had to be borrowed ponies as horses were too large for the surviving Egyptian chariot he used as a model. Breastcollar harness The throat-girth design was not improved until the Chinese breast-strap or "breastcollar" harness developed during the Warring States (481–221 BC) era in China. The Chinese breast harness became known throughout Central Asia by the 7th century, and was introduced to Europe by the 8th century. Its first depiction in artwork was on lacquer-ware boxes from the ancient State of Chu. This type of harness put pressure upon the sternum, where the line of traction is directly linked with the skeletal system of the horse, allowing for nearly full exertion. It was in universal use by the time of the Chinese Han dynasty (202 BC – 220 AD), depicted in artwork of hundreds of different carvings, stone reliefs, and stamped bricks showing it featured on horses pulling chariots. This type of breast-strap harness became known in Central Asia and elsewhere with the Avars, Magyars, Bohemians, Poles, and Russians during the 7th to 10th centuries. After Central Asia, the first breast-strap harness was spread to Europe by the 8th century (in depicted artwork), and became more widespread by