Though necessity is sometimes the mother of invention, invention often precedes the creation of necessity and arises cumulatively from creative geniuses building by trial and error on the discoveries of their capable predecessors. In addition, economic incentive and social factor, as well as geographic factor plays a role in diffusion of technology leading to development of technology that differ from culture to culture. .
Diamond stated that people driven by curiosity and love of tinkering developed many or most inventions. Once a device had been invented, the inventor then had to find aplication for it. Some other devices, invented to serve one purpose, eventually found most of their use for other, unanticipated purposes. For example, Thomas Edison's phonograph. When he developed phonograph, he wanted it to be used for preserving the last words of dying people, recording books for blind people, announcing clock time, teaching spelling, etc. reproduction of music was not one of the uses. However, later, jukeboxes were created by arranging for a phonograph to play music at a drop of coin. Through this and several other example in the text, diamond states that invention if often the mother of necessity, rather than vice versa. .
Ideally, its been thought that invention that arise without any precursors are the best inventions, but in reality all famous inventors had capable predecessors and successors and made their improvements at a time when society was capable of using their product. Diamonds also mentions that technology develops cumulatively, and that it finds most of its uses after it has been invented. He mentions that knowledge and technology is acquired by observation and by trial and error. He uses New Guineas, where he takes them to work with him in area away from their home. He notices that they constantly picks up unfamiliar things in the forest, and tinker with them, and occasionally find them useful enough to take it home.