New neurons cannot be created in an adult brain (only new synapses), so over the years it's a very slow process of brain atrophy where neurons that die for any reason cannot be replaced. That already makes indefinitely untenable in a messy living system, since many of the inportant bits can't regenerate.
And then neurodegenerative diseases are really hard bugs to fix, those are the fast brain atrophies where you get motor problems, amnesia, impaired cognition, dementia, and so forth.
Avoiding stroke and hypoxia is one thing, but keeping the cell and protein machinery running and self-healing forever without any deadly bugs is a tough ask. It's only optimized to reproduce, not to live forever
That isn't strictly true. New neurons do get created in adult humans, in at least two regions of the brain, but probably more. There is even some evidence of cannabis potentially contributing to this process.
That very Wikipedia article says that adult neurogenesis essentially does not exist in humans, according to the latest studies.
This used to be a very controversial topic, and some people still hold on to the older view, but new research has found nothing in the last place where it could have been plausible.
And then neurodegenerative diseases are really hard bugs to fix, those are the fast brain atrophies where you get motor problems, amnesia, impaired cognition, dementia, and so forth.
Avoiding stroke and hypoxia is one thing, but keeping the cell and protein machinery running and self-healing forever without any deadly bugs is a tough ask. It's only optimized to reproduce, not to live forever