Question: Why do humans have a age limit, why can't we live for 200, 300 years?

Rebecca Cook answered on 19 Jun 2013:

Humans have an age limit because of something called the Hayflick limit. This limit describes the number of times a human cell divides before it stops. Human cells can only divide a limited number of times and this is because of how DNA ends are protected within cells. DNA within human cells are wrapped tightly in structures called chromosomes (there 23 pairs of chromosomes in a normal human cell). The end of chromosomes (called telomeres) protect the DNA but every times a cell divides they get a little bit shorter until eventually they cannot get any shorter and the cell will stop dividing.

This means we can’t live for 200 or 300 years, scientists know of ways to overcome this limit, however it leads to cancer.