Genetic experiments - the engine of the evolution

Throughout many centuries the mankind observes and studies the nature, trying to solve its secrets and to exploit its laws. We build dams on the rivers, we create Artificial intelligence, we use tools for pro-feeding of. But at the same time we refer the inventions to category of the unnatural. Why so occurs and as far as this distinction is useful? Definition "unnatural" in the dictionary says that it that differs from things which usually are available in the physical world or the nature. However, to define that is "usual", it appears a difficult task...