800 Lifespans Bridge 50,000 Years

Eight hundred life spans can bridge more than 50,000 years. But of these 800 people, 650 spent then lives in caves or worse; only the last 70 had any truly effective means of communicating with one another, only the last 6 ever saw a printed word or had any real means of measuring heat or cold, only the last 4 could measure time with any precision; only the last 2 used an electric motor; and the vast majority of the items that make up our material world were developed within the lifespan of t...

 Different Cells are Replaced at Different Rates

Different types of cells have different lifespans, e.g.:  we shed our skin cells about every 35 days red blood cells live about 120 days, platelets 6 days and white cells less than a day most of the adult skeleton is replaced about every 10 years the average age of a fat cell seems to be about 10 years a 25-year-old heart replaces about 1% of all its cardiomyocytes (heart muscle cells ) over the course of a year, while a 75-year-old heart replaces about half a percent our neocorti...