In modern society, one parent may take a daughter to ballet class and fix dinner so the other parent can get to exercise class before picking up the son from soccer practice. To an observer, they seem to be cooperating in their very busy, co-parenting, monogamous relationship. These people may think they are part of an evolved society different from the other mammals that inhabit earth. But their day-to-day behavior and child-rearing habits are not much different than other mammals who hunt, forage for food, and rear and teach their children, researchers suggest.

Each episode of the newly released second season of "13 Reasons Why" starts with a warning from the actors that the show tackles tough topics like sexual assault, substance abuse and suicide. The warnings, and a downloadable discussion guide provided by Netflix, come out of research recently conducted by Drew Cingel, a assistant professor of communication at the University of California, Davis, with colleagues at Northwestern University.