system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why exactly do people get nauseous (and sometimes puke) from seeing other people puke?

Got the idea from another puke ELI5 post.

Is it a result of humans being social creatures, trying to protect ourselves from toxins we may have ingested as a group/ illnesses we may have picked up, or is it a biological response (or both)?
gpt
>Is it a result of humans being social creatures, trying to protect ourselves from toxins we may have ingested as a group/ illnesses we may have picked up, or is it a biological response (or both)?

Those are not really two different things. The fact that this response has evolved tells you that there's most likely a survival advantage to it, and your hypothesis is very likely to be the cause (bad food ingested as a group).

So if you imagine a large number of people, half of which have a physical response to the smell/sight/sounds of another human puking and another half that don't, it's easy to see why the former group may be less likely to die of food poisoning, and why this physical response may be part of our biology as a result of us being social creatures.

It's also interesting to note that humans respond similarly to other stimuli that may signal danger, such as the smell of feces or rotting flesh, both of which would indicate the presence of harmful bacteria.