Check this out. That old line about the body remaking itself every seven years gets more complicated the closer you look. Live Science lays out the case: skin and gut lining seem to turn over fast, but tooth enamel, the core of the eye’s lens, and stretches of the brain appear to hold on much longer, maybe from the start.
If that holds up, there’s a real possibility that somewhere in a man born in 1964, there’s lens tissue older than his first steps. Interesting claim. Take it with the same discernment you’d bring to anything else.
A cell biologist quoted in the piece suggests even the parts that can renew may only do it in part over a lifetime.
From the Source
Live Science, “Does the human body replace itself every 7 years?”
Source: https://www.livescience.com/33179-does-human-body-replace-cells-seven-years.html