Very fascinating read. Reminds me of a recording of a stream I was listening to recently where the person talks about the idea of death being given in a deal to biological life.
Maybe immortal organisms did exist at one point. Issue is that being immortal prevents you as a specie to adapt to changes. Death of individuals can be simply seen as a competitive advantage within the framework of the theory of evolution.
The linked talk explains that death isn't necessarily related to adaptation. There are many advanced organisms that just keep splitting and don't die, unless eaten or something. Moreover, the part of ourselves that accumulates adaptations (the line of germ cells passed from parents to children) also keeps splitting and doesn't die.
Rather, the point is that at some point the immortal germ line found a weird trick: "let's make in each generation a bunch of cells that will help the germ line reproduce, but that won't themselves reproduce". Like sterile worker bees. And our body, including the brain, is a pile of just such disposable cells.
That’s right, thinking about your point, with cancer our cells still know how to turn immortal. But what’s the point if it’s at the expense of their carrier. I need to reflect on the implications.
On the end a "competitive advantage" is a thing that helps to nicely explain a lot of things like vision, self-consciousness, feelings… Does nothing to the reason why Von Neumann machines appeared on our planet thought.
"The Selfish Gene" attempts to explain this, starting with self-replicating (IIRC) predecessors of amino acids in the primordial soup, which became more and more complex. It's been a while since I read it, so I don't recall details any more.