When an animal helps out another animal, it usually gets something valuable in return. For a long time, many scientists thought that only people could behave generously just because it feels good. This kind of behavior is called altruism. A new study...

Using tools -- all humans do it Whether it's a hammer to install shelves in your bedroom, or a wrench to fix the wheels on your skateboard, you've probably used tools on many occasions throughout your life. In the past, most...