Flying High
Animals were used for those initial trips into space. The US and USSR experimented with different creatures. Not counting whatever bacteria was on the rocket, the first live things were fruit flies because the Americans hoped to see how radiation affected living beings.
Monkey Business
Over time, more complex creatures went into space. The Americans sent Albert II, a rhesus macaque up there in 1949. He was the first mammal ever to leave Earth’s atmosphere. While he survived the launch, he ended up dying on the way home.