The earliest people who lived in North America shared the landscape with huge animals, the so-called “megafauna”. On any given day these hunter-gatherers might encounter a giant, snarling saber-toothed cat ready to pounce. They could see a group of mammoths stripping tree branches. Maybe a herd of giant bison would stampede past. All of these creatures went extinct about 13,000 years ago, likely due to a combination of climate change and over-hunting. Indeed, evidence from ancient North American sites shows American Clovis hunter-gatherers at least occasionally killed or scavenged ice age mega…