Ever wondered why cats consented to live with humans? While they have not been domesticated for as long as dogs they have been sharing our households for thousands of years. The Egyptians were not the first to take them into their homes. They were just the first to decorate their homes, temples and tombs with depictions of them so ensuring their favourites endured for eternity.
African wildcats moved into farming settlements to control pests in stored grain. When vermin were in short supply the cats relied on humans to supply their meals. The cats that survived combined good hunting ability with the ability to reward people with their company. As time went on these cats extended their feline family bonds to include humans and humans reciprocated taking the most tractable and attractive onto their hearths.
However, cats retain all the features that make them good hunters. Their displays of emotion are muted. They are not going to shout out if they find something tasty to eat or a comfortable bed. They regard other cats as rivals for food and other resources. Cats are also not going to show fear or pain if a predator or a rival cat is around. This makes it very hard for you to tell when your cat is not well.
It is thought that the purr evolved as a signal from kittens to their mothers to make her stay with them. They are saying “please settle down next to me” in the most inviting way they know.