No wieghts ever. Definately not genetic.
I don't think working them every day is a big deal. What is the worst that happens? They stop growing? In that case you just wind up with a rock solid 8 pack.
My ex does the same workout routine every single day twice a day! She barely eats. She is shredded. More so than fitness and figure girls and she looks like that 24/7/365. Her muscles are rock solid too. 100% natural! I think sometimes people rely WAY too much on science. Lets face it, every single diet on earth will make you lose weight but the majority of people will say they don't and tell you why. If you want something just work for it. Its the old fashioned way for results!