Our self (Soul), as a form of God's joy, is deathless. For his joy is amritham, eternal bliss. We know that the life of a Soul, which is finite in its expression and infinite in its principle, must go through the portals of death in its journey to realize the infinite.
Although when Christianity appeared the total population of the planet was only a fraction of that of the twentieth century, most of the earth's surface was quite outside the Mediterranean world, Persia, India, and China.