"e.g." is an abbreviation for "for example".

So, "I doubt we'll wipe out, for example, ants as a class".

Meaning that the comment wasn't particularly about ants, just used them as an illustrative example.

"e.g." is for lists of examples. not just one.

Not necessarily. As I understand it, it indicates the presence of a list or group, that the subject(s) mentioned after it belong to. The location of e.g. in the sentence is unusual though: usually it will be found at the end.

No, it's just an abbreviation, nothing more.

I'm not a native speaker.