5000 to 2000 BC Pastoral Period Rock Painting, Libyan Sahara via Libyan Soup's flickr site
Just read a fascinating article at The Atlantic by Megan Garber about a new theory by anthropologist Pat Shipman that 35,000 years ago dogs helped humans flourish as Neanderthals died out. Shipman argues that man and dog created a "virtuous circle of cooperation — one in which humans and their canine friends got stronger, together, over time."
Highly recommend full article.