As a general rule, the latest one. As much as it can be hard to see, life on average has been improving. Why would I want to go back in time where medicine was worse? Or we were covering everything with asbestos, or whatever was going on at that time. The only metric that I can think of that has been getting continually worse is the climate situation. Humans are pretty awesome though and I expect that we will be able to mitigate the worst parts for us. Note: That doesn’t mean that we shouldn’t be actively trying to stop it.