In Skin in the Game, Taleb writes:
If humans were immortals, they would go extinct from an accident, or a gradual build-up of misfitness.
According to the Bible, this is, indeed, what happened. When humans could live to be almost 1000 years old, we got so bad that God had to wipe the slate clean with the Flood. Something similar happened with the Tower of Babel. Lifespans had begun to shrink, but one of Noah’s sons still lived for 600 years, and mankind had to be dispersed. Otherwise, the evil they would be able to accomplish would be considerable.
As God says in Genesis 11:6:
And nothing that they propose to do will now be impossible for them.
The question is often asked, “What could we do as a race if we could increase our lifespans by several orders of magnitude?” The accumulation of wisdom and experience would accelerate our development and allow us to do great things.
And yes, we would be able to do great things. Great things that would be in service to greater and greater evil.
We are a fallen race, and while we are in these corruptible bodies, longer life would only exacerbate our corruption. What we need is a new type of life. What we need is new creation, not old creation stretched out and scraped thin.
Immortality would literally lead to our extinction. Banishment from the Garden was a punishment, yes, but like all discipline from God, it was also a grace. The reasoning given for our banishment is so we would not reach out our hands, eat of the tree of life, and live forever.
In The Magician’s Nephew, C.S. Lewis also hints at this truth. Jadis, the evil queen who would become the White Witch of The Lion, the Witch, and the Wardrobe, takes fruit from a garden in Narnia and gains everlasting life. Many today would consider this a victory. We are obsessed with long life, chasing after it like the Coyote chasing Roadrunner, with similar results.
And yet Lewis says Jadis is doomed to misery.
But length of days with an evil heart is only length of misery and already she begins to know. All get what they want; they do not always like it.
Death is the great enemy, yet the type of immortality we seek would lead to a half-life, the kind where we use fangs to suck blood. If disease and death were conquered, Man would still be a sinful creature, only more terrifying and miserable, able to take their misery, multiply it, and spread it across the universe. Can you imagine a Stalin who lived forever, and there was no way to get rid of him?
Without Christ, immortality is a curse.