Thank you all for your great answers and new insights into this topic.
Regarding the giants, I have a question about the calories it would take to keep them going: Is it true that the larger and taller a human or animal body is, in general a larger number of calories are needed to keep them going or not necessarilly? I read that for humans in the eight foot tall range and above, some of them would have to have a daily consumption of at least 8000 calories or something huge like that to maintain their health.
Can you imagine the dietary consumption of a group like that? Wow. They would be eating meat and carbs galore.