Dogs and humans have been in a symbiotic relationship longer than history can document. Dogs naturally became more domesticated as humans did, and have been more or less selectively bred for a few thousand years.

Dingos are different. No one knows for certain how domesticated they were when they first came to Australia. They probably had been domesticated enough to come on boats with the first humans to migrate to Australia. After arriving in Australia, they became feral, although still symbiotically migrating with humans. They are now considered a native species of Australia.

Many species of plants have lived symbiotically with humans as well. As long as humans have been living with dogs, they have been domesticating and breeding plants. As plants were more extensively bred, they became more dependent on humans for their perpetuation. Some are so overly bred that they are sterile and unable to perpetuate without human…