This matters a great deal, because knowledge enables fundamentally different modes of problem solving and progress. Humans can select and combine knowledge created by other humans, allowing small changes to accrete into large bodies of work over time, which in turn provide the basis for scientific and artistic breakthroughs. Without knowledge, other species have only two methods of sharing things they have learned: communication and evolution. Communication is local and ephemeral, and evolution is extremely slow. As a result, animals and plants routinely encounter problems that they cannot solve, resulting in disease, death and even extinction. Many of these problems today are caused by humans (more on that shortly).