How long have we had pet doors? Sir Isaac Newton is often accredited with inventing the pet door, but humans have had holes in walls for their pets for thousands of years. It’s hard to estimate how long ago the oldest pet door would have been built, but we do know both dogs and cats have accompanied humans for millennia. Dogs are believed to have been domesticated for at least 12,000 years – and cats domesticated themselves at least 9,500 years ago. The first known domesticated cats were on Cyprus around 9,500 years ago, but that doesn’t mean our feline friends didn’t keep us company before that time. In the beginning, the cat door was a hole in the wall. Geoffrey Chaucer describes a cat hole in his 14th century Canterbury Tales – a servant knocks on a door, no one answers, and he peeks in through the cat hole. Exeter Cathedral allegedly has a clock tower with a cat hole carved around the year 1600. Sir Isaac Newton does have a role in the development of the pet door. He is the first person known to have covered the cat holes and probably the inventor of the modern cat flap – he hung felt over the holes to keep excess light from coming in.