system
Given the following post, respond as if you're commenting on Reddit:
human
[The Martian] why would the poop bags be labeled by the person?

Rewatching the Martian with my wife and we noticed that there is a scene indicating mark watney pooped and flushed, and there was a list of names on the wall. Then he uses the poop for fertalizer and apparently knows who pooped in each bag. Why would NASA possibly want to know who pooped in each bag?
gpt
To check the feces for any change. Every venture into space is milked for any and all scientific discoveries possible, considering how expensive it is to send just one person, much less several. So those bags of feces are studied for inconsistencies, nourishment, and anything that could require looking into.