Many open source developers agree that the Linux kernel was not designed but rather evolved through natural selection. Torvalds considers that although the design of Unix served as a scaffolding, "Linux grew with a lot of mutations - and because the mutations were less than random, they were faster and more directed than alpha-particles in DNA." Raymond considers Linux's revolutionary aspects to be social, not technical: before Linux complex software was designed carefully by small groups, but "Linux evolved in a completely different way. From nearly the beginning, it was rather casually hacked on by huge numbers of volunteers coordinating only through the Internet. Quality was maintained not by rigid standards or autocracy but by the naively simple strategy of releasing every week and getting feedback from hundreds of users within days, creating a sort of rapid Darwinian selection on the mutations introduced by developers." Bryan Cantrill, an engineer of a competing OS, agrees that "Linux wasn't designed, it evolved", but considers this to be a limitation, proposing that some features, especially those related to security, cannot be evolved into, "this is not a biological system at the end of the day, it's a software system."