In the Renaissance, wealthy aristocrats showcased exotic beasts in private menageries. Safely caged, animals inspired the interest of naturalists and fed the curiosity of the masses. By the 19th century, increased urbanization and colonization aided the expansion of zoos in which animals were tamed to serve as domesticated livestock. Nowadays, with many natural habitats under threat of extinction, the social function of zoos is less clear. Such institutions both present the illusion of wild animals in a natural state to a nostalgic public and find themselves justifying their existence as saviors of endangered species.