On the same theme of the previous post (the dynamic steady state of our bodies), another thought may be entertained.
Our bodies are changing all the time and are in a tightly controlled balance with the environment. Every substance in the body is continuously lost and replenished. The input equals the output and the body remains in a steady state. Water which composes more than 60% of our bodies is lost through the kidneys, skin, lungs and intestine. It is replaced by the water we drink, water in our food and water produced in our bodies as a result of food metabolism. The water in our bodies today is not the same water that was in them days or weeks ago. The same thing applies to other elements and compounds that compose our bodies. Everything is lost and replaced by a new thing continuously. After a time the whole body has been replaced keeping the same design; the same architecture imposed and governed by our genes. Slow and gradual changes in design occur as a result of aging. Rapid changes occur sometimes as a result of disease and accidents. In other words every one of us is not exactly the same person he was sometime ago. He is a copy of his previous self. If you see a friend that you have not seen for a year you are in fact not seeing him but seeing a copy of him! To be more precise a copy of you is seeing a copy of him!! A somewhat disturbing idea to sleep on if you are reading this article late at night.