Greyhounds are one of the most ancient breeds of dogs, and appear in art and literature throughout history. In ancient Egypt, Greyhounds were mummified and buried along with their owners, and tombs were often decorated with Greyhound figures. Greyhounds have a very gentle and quiet disposition. Aggressiveness towards other dogs and people has been nearly eliminated from the breed. Greyhounds are sighthounds, a group of hounds that pursue their prey by sight rather than scent. In spite of this, it is possible for Greyhounds to peacefully coexist with other pets, however some do retain a strong prey drive and are sometimes unsuitable for houses with small pets. Greyhounds need less exercise than you would think. They are primarily a sprinting breed, rather than an endurance one. They are happy with a few good runs a week and are quite content to spend a lot of time lying around, thus earning the title of "45mph couch potatoes". They are typically a healthy and long-lived breed with an average lifespan of 10 to 12 years. They do not have undercoats and are less likely to trigger dog allergies in humans.