If we think that Adam is only an ancient mythological figure then there's a good chance we treat Jesus the same way because in the Story of Scripture they are connected. If you reject the Genesis story that claims we are all descended from Adam and Eve and instead you believe that we are the product of probabilities and chance and that matter and energy are eternal, then this is the "story" you believe gives meaning to your life. So at your funeral, if you have one, where will the hope come from? Is humanity and the world actually progressing? If you're only a glob of energy and matter that by chance coagulated together in a complicated mass of cells we call life and now the life is gone, why should anyone grieve over losing you? Ecclesiastes does present the thesis that this life is all there is and it drives this presupposition to it's true conclusion. We are all only a breath and at death we're only dust. But Ecclesiastes points us to our Creator who actually is the One who gave us the gift of life. And Jesus is the One who never became a pile of dust. He rose again and He promises those who believe in HIm that not even death can separate us from the love of God we've found in Him. Jesus is the only true source of progress and hope.