"The chicken is not human."
Translation:Το κοτόπουλο δεν είναι ανθρώπινο.
The Greek sentence seems rather strange - it does not express that the chicken is not a human being. Ανθρώπινος, -η, -ο is either used in constructions like η συμπεριφορά του δεν είναι ανθρώπινη - his behavior is not human(e) (i.e. civilized, compassionate etc.), or in combinations like το ανθρώπινο σώμα, η ανθρώπινη μοίρα, η ανθρώπινη δικαιοσύνη etc. [There is another also another sentence in this course Η γάτα είναι ανθρώπινη.]
Yes, actually ανθρώπινος means: that belongs to or is proper for a human being.
I thought I heard somewhere that κοτόπουλο referred to a cooked chicken as food, rather than a live chicken, which has a different word. Was I mistaken about that?
For the live animal you can use either κοτόπουλο (= young chicken irrespective of gender) which is also used when talking about food, or κότα = hen. So when someone has chickens you can say 'έχει κότες' in general. The rooster is κόκκορας. You can see more about gendered nouns for animals here https://forum.duolingo.com/comment/27198534.