Human civilization relies on biodiversity in many ways. Sudden changes in species biodiversity result in environmental changes that can modify weather patterns and therefore human civilizations. Humans are dependent on agriculture, which developed when ancestral humans found species that made suitable foods. At least 11,000 years ago, humans started to select plant and animal species to be cultivated on farms. Going back for thousands of years, humans have been artificially selecting species for food, building materials, textiles, and medicine. That progress is ongoing. Human ingenuity continues to benefit from studying the natural world and either directly using or modifying materials and compounds for industrial use. Maintaining the current level of biodiversity will make it substantially more likely that discoveries can be made. New Discoveries For example, in 1969, Thomas D. Brock and Hudson Freeze were studying the Lower Geyser Basin of Yellowstone National Park and discovered a strain of bacteria that is surprisingly heat-tolerant. From this bacteria, an enzyme called Taq polymerase was isolated. This enzyme allows researchers to perform polymerase chain reaction (PCR), which underlies most biotechnological advancements that revolutionized the production of pharmaceuticals, food, and consumer goods among others. For some, discoveries that benefit humanity are the strongest argument for human responsibility in maintaining biodiversity; others take a less human-centered view, arguing that biodiversity must be protected for its own sake. Since human activity has diminished biodiversity, it is our responsibility to minimize the damage.