Add Yahoo as a preferred source to see more of our stories on Google. Japanese macaques at Joshin-etsu National Park in Japan. (Peter Adams / Getty Images file) (Peter Adams) Humans are far from the ...

Same-sex behavior is common across the animal kingdom—more than 1,500 species are estimated to have been observed engaging in same-sex behavior, from spiders and nematodes to bonobos and fish. Still, ...