Does Altruism Actually Exist?

The concept of altruism has been around for a long time, and for almost as long researchers have argued over the meaning of it. Some have suggested that true altruism doesn't even exist. After all, helping out someone else generally involves some cost or risk to you: either you're expending valuable energy or you're putting yourself in danger, all for the well being of another. Evolutionarily, this doesn't make a whole lot of sense, since we're all out to preserve ourselves -- and our genes. There must be something else going on.