Now that we have wheels, blades and clothes, what were early humans to do with all our cool stuff? Just carry it around all day? No. We needed one more breakthrough to make life a little easier, if not actually save human existence. (Also, disclosure: None of those discoveries happened in that order.)
That brings us to shelter. Now, let's not pretend that shelter is a unique breakthrough that only humans discovered. We definitely started off like most animals -- just finding a good place to hide. For our early ancestors, that probably even meant living in nests in trees. Of course, caves and rock outcrops were probably popular choices, too.
As long as 2.6 million years ago, there were signs that early human groups began collecting food and tools to bring them back to certain favorite watering holes or sleeping spots [source: Smithsonian]. About 800,000 years ago, we start seeing fire and hearths added to the mix. But our earliest evidence of a man-made shelter comes from 400,000 year-old postholes and other archaeological evidence in Terra Amata, France [source: Smithsonian]. By building shelters, humans were not as vulnerable to their environment and could survive harsher conditions.