In the first half of the show, the world's foremost authority on human-animal interactions, Hal Herzog, joined Ian Punnett to discuss the complex relationships people have with animals. Herzog said he initially became interested in this field of study after meeting neighbors who engaged in cock fighting with seemingly no moral qualms about it. "I realized that their justification for fighting chickens wasn't that much different than my justification for eating them," he explained.

Herzog presented a fascinating thought experiment in ethics, his version of the trolley problem, by which he illustrated the contradictory attitudes people have concerning animals. In the problem one must choose between saving a group of animals or a human being. A person always chooses to save a member of their own species over an animal, he explained. Yet, those same people will spend fortunes to care for their pets instead of giving money to charity to save suffering humans, he added.

So why do people fall in love with some animals and hate others? According to Herzog, certain features, such as the large eyes of a baby seal, bring out a caring parental response in humans. Beady-eyed snakes, on the other hand, are almost universally disliked by people, he said. The human-animal bond may go even deeper with dogs, Herzog continued, pointing out that people have co-evolved with canines for some 14,000 to 40,000 years. Having been domesticated for so long, dogs can read human facial expressions and mimic particular behaviors, he noted.

But dogs are not considered pets everywhere on the planet. In Asia, 25 million dogs and cats are eaten each year, Herzog revealed. What one culture considers food, another may consider taboo -- it's arbitrary, he said. "We sort of conveniently construct categories that enable us to use animals in ways that we find intuitively satisfying," he observed. Herzog also shared why he gave up fishing for sport and why he can no longer morally justify hunting. Most hunters do not kill to eat, they eat because they have killed, he said.

Researcher James Chiles provided an update on the Chilean mine rescue in the third hour. The final 90 minutes of the program was devoted to Open Lines.