People often speak of donkeys in belittling terms. You may have heard the expression, "I'm just someone who has to do all the donkey work." Or "So-and-so is as stubborn as a mule" (a mule is part donkey). These sayings overlook the contributions of a truly valuable animal. Donkeys have served the human race for thousands of years. They were once prized as symbols of humility, gentleness, an…