Let's take a look at this short passage :
Cats of all kinds are present in the legends, religion, mythology, and history of (1) MANY different cultures. Cave paintings created by early humans display different types of wild cats (2) WHO/THAT are now extinct, or no longer around. Many of these great beasts saw humans as food, but were hunted by humans (3) IN return.
The key for (2) is WHO/THAT , and it is explained that :
Used after a noun to show which person or which people you are talking about:
The girl who(that) I met in Italy send us a card.
But different types of wild cats are animals. Is using WHO possible ?
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
I wouldn't use who in that context for wild animals, but I would happily use it for something like a pet dog or cat.