Since the 1960s, conservationists have had a standard solution for saving biodiversity: Protect natural areas from human influence. But a new analysis of Earth’s land use going back 12,000 years suggests that even in the time of mammoths and giant sloths, just one-quarter of the planet was untouched by humans, compared with 19% today. Because some of those inhabited areas are now biodiversity hot spots, people probably helped sustain—and even increase—the diversity of other species for millennia, the authors write. The findings also suggest many traditional practices and Indigenous peoples play a key role in preserving biodiversity.