Quote Originally Posted by SwirlyMass
i dont understand! did they think you kept the exact same brain cells until you die?

i think scientists would be a little smarter than that. especially since ive always heard that after one year there is not a single original cell left in your body, they've all reproduced and died.
It's true. All the cells that were in your body seven years ago have died and been replaced by new cells. This reminds me of something Richard Dawkins said in this talk of his:

"Steve Graham points out that you and I are ourselves more like a wave than a permanent thing. He invites us, the reader, to think of an experience from your childhood, something you remember clearly, something you can see, feel, maybe even smell as if you were really there. After all, you really were there at the time, weren't you? How else would you remember it? But here is the bombshell: you weren't there. Not a single atom that is in your body today was there when that event took place. Matter flows from place to place, and momentarily comes together to be you. Whatever you are, therefore, you are not the stuff of which you are made. If that doesn't make the hair stand up on the back of your neck, read it again until it does, because it is important."