'The question of why we die is an excellent one

This question can be answered both from religious point of view and biological point of view.

Firstly,as a Christian that I am ,we were taught from the Bible that when Adam sin by disobeying God,he lost his immortality and thats when death came into this world and that's why we grow old and die .This is from Christian belief .

Let's see from biological explanation why humans die.

here are some previous arguments and why they are wrong.

Myth 1: We die to make room for younger generations.

Genes are selfish, and each individual body is a vehicle for a collection of genes. These genes are selected to favor the survival of copies of themselves. Since parents and offspring use the same resources, the death of a parent creates room ecologically for just one offspring. Each gene in the parent has a 50% chance of appearing in this offspring. But it has a 100% chance of appearing in the parent, because it’s already there. It’s never, then, in the evolutionary interests of a parent to die so an offspring can replace it.

Myth 2: We die because our cells/DNA get damaged with age.

This is like saying bad drivers die because of blood loss. It’s a proximate mechanism of death, not the evolutionary cause of mortality. Our somatic cells (the cells that are part of our body) do indeed suffer occasional mutations as they divide. These mutations can kill or damage cells, which is annoying but not generally a big problem as we can make more. However, the worst mutations do something much more dangerous: they help cells to survive and proliferate. That’s how you get cancer. Because this risk accumulates over time, cells are normally allowed only a limited number of divisions before they undergo cellular senescence, that is, they die. But the genes that cause cellular senescence can also stop working. So that’s one of the ways in which we get old: our somatic cell lineages get older

Every day of your life, the Universe in effect rolls a pair of many-sided dice. Snake eyes, you’re dead. Every day the probability that the Universe has at some point in the past killed you increases. At some time after your birth, on average, you’re dead.