It is pretty amazing how complicated our bodies are, but I think the expiration date is there to prevent overpopulation - if our ancestors didn't die, the planet would be overpopulated with lazy apes who don't evolve cause there's no need to :-).

Once we're smart enough to fully control ourselves and our environment, immortality becomes an advantage - sadly, I don't think we're there yet...

Edit: by immortality, I always mean living longer than ~400 years. I'm pretty sure it's impossible to live forever (sooner or later, you'll die of an accident anyway), but living longer and living without any disease should be great...

1> Current actuarial tables have us dying by 550-650 even if there was no aging. Stuff like car accidents, slipping in the shower, etc.

2> "I think the expiration date is there to prevent overpopulation" implies evolution has a purpose. You know when you work at a company, and the processes just change over time and change over time and 5 years in no one remembers why you file a tps report before going on vacation? That's what evolution is like: Whatever processes happened to survive. That TPS report may have some value, it may be easily replaced by a more logical item, or it may be completely useless. Just the fact the process of filing a TPS report before leaving for vacation exists, doesn't mean it's necessary for the health of the organization.

3> Populations the world over are manually dropping their procreation rates to near replacement levels. I'm sure many people would drop it further if they had a few hundred extra years. http://www.guttmacher.org/pubs/journals/3201400.html

>>It is pretty amazing how complicated our bodies are, but I think the expiration date is there to prevent overpopulation - if our ancestors didn't die, the planet would be overpopulated

That is an argument based on group evolution, largely disproved (some unusual edge cases might exist).

I'd recommend reading "The Selfish Gene", it is an incredibly fun journey in beautiful English (Disclaimer: I'm a non-native English speaker.) It will probably change your world view.

I was assuming, of course, that the drive to reproduce would still be there - but, yes, on a closer look, the reproduction rate would diminish, while evolution would continue for the existing individuals...