system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If it is highly risky to give birth after 40, why do women continue to have periods into their 40s or 50s?
gpt
In it's simplest form evolution works on a basis of "how likely is this mix of DNA to produce offspring to carry on to the next generation".  

Evolution doesn't really care if you live long or not, only that you pass on your DNA as much as possible. Generally speaking someone who lives longer will have more chances to do that, even if the risk of death increases. So it wouldn't build in a process to stop the cycle early, because that drops your chance of passing on DNA to 0.