"[Why a cell vs a gene or partial gene?] There's been plenty of work done on RNA replicators and they have a tendency to become smaller and simpler and effectively better able to make copies of themselves with whatever you provide them in the environment, and they end up with a thing called , which is basically the binding sequence of the which allows it to furiously replicate away. ...If you're providing in the environmwent an RNA polymerase and an infinite supply of s then... they become simpler and simpler, and faster and faster at copying. ...The trouble is there isn't ever going to be an environment that's providing that for you except in a cellular context... If you're selecting at the level of genetic replication, the replicators that are better able to make copies of themselves fast are those which are, in effect, the most selfish and the least likely to cooperate to try and convert the environment into ."