I hate to be the wikipedia poster here, but the entry on Biological Immortality does make for a good read in this context;<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Biological_immortality" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Biological_immortality</a>