The two central ideas of evolutionary theory are (1) that all organisms – both those currently living and those that have ever lived on Earth – are related through descent from common ancestors; and (2) that they have evolved or died out through natural processes. Simply put, evolutionary theory suggests that we are part of this world; we are one biological species among numerous others, with which we are more or less related, having diverged from our common ancestors over time. However, many people do not accept these ideas. They think that if we accept that we are animals, we are devalued and human morality is threatened. They also think that if we accept that life has no inherent purpose, this deprives it of meaning. For these people, evolutionary theory is a rather nihilistic idea, and this is where many of them see the conflict between evolutionary theory and religion. This conflict is also perceived by those proponents of evolutionary theory who are irreligious or atheists, and who also think that evolutionary theory has been the death blow of religion.