7 year olds having SEX!!!!

I just came across a note from one of my other sites and the lady and her mother caught two 7 year olds Naked and He was on top of her!! For some reason this doesn't surprise me, but yet, why go as far as that..... I just don't see why this is happening at younger ages anymore and getting really scary... My son is 6 and when he was younger I would catch him wiggling and he told me he wanted "it" bigger. I just took it as learning, experimenting with his body but i am now afraid it may become something more as he ages and girls... How would you take this situation? 1. experimenting 2. seen on tv or someone "doing it" 3. having it done to them?