People who doubt that some kind of soul or spirit really survives their death therefore strive to leave behind something a bit more tangible. That 'something tangible' could take one of two forms: cultural or biological. I might leave behind a poem, say, or some of my precious genes. My life has meaning because people will still read my poem a hundred years from now, or because my kids and grandchildren will still be around. And what is the meaning of their lives? Well, that's their problem, not mine. The meaning of life is thus a bit like playing with a live hand grenade. Once you pass it on to somebody else, you are safe.