Steven Tyler says he is a bad advertisement for the dangers of drugs.The Aerosmith rocker, who is in good health despite his drug and alcohol-fuelled past, says the secret to his youthfulness is good genes. He told Britain's Independent newspaper: "People always look at us and think, 'OK, they got away with it - why shouldn't I? The truth is it's all in the genes. My Italian grandfather on my mother's side had a full head of hair in his old age, and my paternal grandfather was this wiry Portuguese sailor."Tyler - who was persuaded to check into rehab by his bandmates and manager Tim Collins in 1981 - admits drug use almost ruined his career. He said: "Of course I did way too many drugs. I sunk to my knees and lost everything, but I'm part Italian and my good old-fashioned guilt came up and I had to check in to rehab. The only way out is through."Unlike some performers whose vocal cords are destroyed through drug use,Tyler can still belt out notes in his upper ranges and says rehab saved his voice. He said: "When I was doing heroin it gave me a gravely voice and I just couldn't hit the notes, but I'm clean now of course. I take great pride in not chickening out on the big notes."Aerosmith are headlining Hyde Park Calling, their first full-length UK tour in eight years this weekend.