A boy and his dog, c. 24,000 BC

"One day around 26,000 years ago, an eight-to-ten-year-old child and a canine walked together into the rear of Chauvet Cave, in what is now France. Judging from their tracks, which can be traced for around 150 feet across the cave floor, their route took them past the magnificent art for which the cave is famous and into the Room of Skulls—a grotto where many cave-bear skulls can still be seen. They walked together companionably and deliberately, the child slipping once or twice, as well as stopping to clean a torch, in the process leaving a smear of charcoal.
     "It’s nice to imagine that the pair’s Huckleberry Finn–like exploration became the stuff of legend in their clan, for at the time Chauvet Cave’s recesses were abandoned, its art and cave-bear bones were already thousands of years old, and soon thereafter a landslide would seal the cave entrance. Whatever happened, the pair’s adventure certainly became famous in 2016, when a large radiocarbon dating program that included the smear of charcoal discarded by the child confirmed that the tracks constitute the oldest unequivocal evidence of a relationship between humans and canines."

     Tim Flannery, "Raised by wolves," The New York review of books 65, no. 6 (April 5, 2018):  16 (16-20).  Though there could well be corroborative detail in one of the books under review, Flannery's only footnote is to this article, in which, however, I have yet to locate an obvious reference to the child-and-canine specifically.