Hmmmm??? This spiked the question about how often we humans shed our parts and get renewed, so here's the short answer: "Red blood cells have a lifespan of just 70–120 days, while white blood cells live on average more than a year. Skeletal muscle cells last around 15 years. Skin cells live about two or three weeks. Colon cells die off after about four days. Sperm cells have a life span of only about three days, while some cells never get replaced at all. These include neurons in the cerebral cortex and the cells that make up the lenses in our eyes."
I guess this is why our vision deteriorates as we age and doesn't bounce back on its own. And why after 75 years I still remember much of my childhood.
