How did Man’s Best Friend come about?  With 400 million dogs in the world, this question has been asked often.  The more time I’ve spent exploring the question, the more odd answers I’ve found. Humans and their dogs have been best friends for a long time, it seems.  But just how long is a matter of dispute.  Conventional wisdom says that dogs emerged as humans were settling down in villages and beginning agriculture, about 10,000-12,000 years ago. But analysis of mitochondrial DNA (mtDNA) tells a different story. MtDNA in the cells of living things reproduces asexually, and comes only from the mother.  The only way it ever changes is through mutation, and that rate of mutation is slow: about 1-2% every 100,000 years. Studies…