Can humans ever understand how animals think?

Yes, that is a very telling video. Co-operative species have to have fairness for co-operation to work. I saw a documentary a while back about behavioural scientists finding fairness in places they didn't expect. They were tracking cougar and how they behaved, and found in their studies that cougar would sometimes share their kills with neighbours - but that it was much more likely to happen if that neighbouring cougar had previously shared with them.