Question: why do we die?

Iain Bethune answered on 24 Jun 2015:

Everyone dies eventually as the body is not perfect at repairing itself. Even if we keep our heart, lungs etc. healthy eventually the brain will start to fail.

What actually kills you depends a lot on your lifestyle, genetic makeup, when you live. Worldwide, the top killers are Cardiovascular disease (heart attacks and strokes), followed by infectious diseases, and then cancer.