The order of events in space exploration, at least as far as the US is concerned, seems to have followed an interesting logic.
NASA sent several monkeys into the space before it decided to send a man (can't use a gender neutral man/woman here, can I?). The rationale, of course, would have been that monkeys are probably the biologically closest to humans and yet the most 'affordable' life forms at a human's place.
Appollo 8 was the the first manned spacecraft to orbit the moon and was one of the most widely covered events in that decade. The astronauts who were sent after the monkeys took the first picture of the Earthrise. And it so happened that the astronauts who were sent after the monkeys had to spend their Christmas orbiting the moon. In a live telecast during the Christmas eve, the astronauts who were sent after the monkeys tried to make the moment poignant by reading a few lines from the Old Testament that went, "[I]n the beginning God created the heaven and the Earth." (Rest of the quote.)
When the astronauts who were sent after the monkeys returned to Earth, they were sued by atheist Madalyn Murray O'Hair. Even though the case itself was dismissed on dubious grounds, it made sure that NASA sent slightly evolved primates -- not just from monkeys -- in its future missions.