ScienceDaily for July 20, 2010 reported on human attachments to animals as a factor in evolution.
Shipman suggests that the animal connection was prompted by the invention of stone tools 2.6-million years ago. "Having sharp tools transformed wimpy human ancestors into effective predators who left many cut marks on the fossilized bones of their prey," Shipman said. Becoming a predator also put our ancestors into direct competition with other carnivores for carcasses and prey. As Shipman explains, the human ancestors who learned to observe and understand the behavior of potential prey obtained more meat. "Those who also focused on the behavior of potential competitors reaped a double evolutionary advantage for natural selection," she said.