What scientists do is all about human needs, not like Rousseau argued, which is only a result of pride and vanity. For example, do we need cars, trains, planes? No, surly we can walk to anywhere by our own feet, no matter how long it takes or how dangerous it can be. Do we need phones? Of course not, I can yell from one mountain to the other trying to tell my mother I will get home later. Excuse for my sarcasm and please no offense, but I have to quote the criticism from Jules Lemaître who thought the instant deification of Rousseau as 'one of the strangest proofs of human's stupidity'.
Material abundance also brings some problems and the critical one is inequality which is the most important argument arised by Hippies. The conclusion they give is no more material, and we should all go back to primitive or so called as 'noble savage'. Obviously it is an unadvisable and unrealistic idea. Inequality can not be absolutely avoided whether we use forks or not. Once wolves work together for hunting, there is an Alfa as a leader who is the strongest one of the term and will get more food for its protection from enemies. Is that fair for other members gain less because they are born weaker? Should they just abandon eating for avoiding unwanted impurity?
Above all, I can't say agree to Rousseau for his attitude to sciences and ars. If there are any unfairness caused by sciences, what we should do is to creat more material wealth for everyone can afford luxury. There will be no inequality which is the same as primitive society, and the difference is ample material.