A chimpanzee hugs her newborn at Burgers' Zoo in Arnhem, Netherlands, in 2010. Over the course of his long career, primatologist Frans de Waal has become convinced that primates and other animals express emotions similar to human emotions. AFP/Getty Images hide caption
Friend or foe? A California two-spot octopus (Octopus bimaculoides) gives observers the eye at the Marine Biological Laboratory in Woods Hole, Mass. Tom Kleindinst/Marine Biological Laboratory hide caption
A 17-year-old male bonobo eats while his son watches in the Lola Ya Bonobo Sanctuary, Democratic Republic of Congo. Fiona Rogers/Getty Images hide caption
Muslim women praying together in the Istiqlal mosque in Jakarta, Indonesia. Afriadi Hikmal/Getty Images hide caption
A young man records a voice note. A new dating app called Waving lets you swipe right on someone based only off short voice profiles. Getty Images hide caption
Rats and people may rely on "metamemory" in a variety of different ways, scientists say. For a rat, it's likely about knowing whether you remember that predator in the distance; for people, knowing what we don't know helps us navigate social interactions. fotografixx/Getty Images/iStockphoto hide caption
Lily chases sheep for the first time in her shepherd-mix life, at Raspberry Ridge Sheep Farm in eastern Pennsylvania. Several times a year the farm invites dogs for "herding instinct tests." Fred Mogul/WNYC hide caption
Male and female tungara frogs. Among these frogs, the guy with the best call usually wins the gal — except when you throw a third-choice loser into the mix. Alexander T. Baugh/Encyclopedia of Life hide caption
There is no such thing as a free lunch. iStockphoto hide caption
