Death

This site tells the story of the history of the universe. Click Earlier and Later to follow the story.
Note: Many facts have been simplified to make them easier to understand.
Our new free weekly podcast Time Crystal tells this story as sci-fi fantasy

Death has been around as long as life. Early bacteria died because they ran out of food or water or because of hazards in the environment such as radioactivity or the great oxygen poisoning or viruses.
But in general bacteria do not die. Instead they divide into two daughters and so can be said to be immortal. What would happen to a bacterium which did not reproduce? It seems likely that it would die eventually, because of these environmental hazards. Life and reproduction are necessary for a cell to survive. If you click the

Death Later

icon on some pages you can trace through the major causes of death and disease.

Eukaryotes
Eukaryotic cells seem to be programmed to die. The early eukaryotes, such as the protozoa, like bacteria, kept growing and dividing forever. More advanced eukaryotes, multicellulars, had cells which specialized. When cells specialize, for example swimming cells, they loose the ability to reproduce. Eventually they die. So the price cells paid for living together was that some of them died so others could reproduce. Only the reproductive cells managed to escape death.

If living things did not die then

all the carbon in the Earth would get tied up in their bodies, and there would be none left to make the next generation of life
there would be no death of less successful organisms, so evolution would halt
As the living things slowly died off (for example by having accidents) life would gradually come to an end.