Dogs have been shaping—and being shaped by—humans for about 15,000 years, evolving from early partners of hunter-gatherers into an astonishing range of specialized companions. Across the globe, they adapted alongside people to wildly different environments and needs, from powerful Arctic sled dogs and agile rainforest hunters to high-altitude dogs with genetic traits for surviving thin air. Some were even bred for wool, while others played important spiritual or ceremonial roles.