The cross that has been most significant in human history is the one between horses and donkeys to create the mule.
Mules have played a key role in the development of the world.
The mule has been deliberately bred by man since ancient times.
Harness races for mules began in Olympia in 500 BC.
The mule was highly valued in ancient Greece for use as pack animals and to draw carriages as well.
In the Old Testament, the mule replaced the donkey as the royal beast and was ridden by King D.