Entering Space: Creating a Spacefaring Civilization

Humans are not native to the Earth. So posits astronautical engineer Bob Zubrin in the opening of Entering Space. We're native to just a small sliver of it, the spot where our species originated in tropical Kenya. We set out from that paradise about 50,000 years ago, north into "the teeth of the Ice Age," and all the ground we've gained since then has been thanks to our tenacity and our tools.