Mastiffs are one of the oldest breeds of dog on earth. I had an english mastiff that lived for 11 years. He was about 200lbs in his prime. A lot of people don't know how fast these big dogs can run. My parent's driveway is about 5/8 mile long, with a 1/4 mile strait. My dog would run behind me up the driveway, and could keep up with my car to around 35-40mph. He actually ran down a deer one time. He was a very lean mastiff. Another weird thing about my mastiff was that he hated birds. If he saw a buzzard or even just a shadow of a buzzard he would go crazy.