Dogs and humans share a profound affection for each other. Dogs give infinite love to humans; sometimes, that love becomes the motivation to live for people. T wo main reasons lie behind this firm relationship between the two species: a lasting friendship throughout history and an irresistible physiological interaction.   When did the relationship between dogs and humans begin?  About 30,000 years ago, some wolves began scavenging food near humans. Humans offered these wolves food and...