For your first paragraph, yes, I did choose just one century because I am aware that our behavior has changed over our history, many times.

edit: Just to provide an example, we used to genocide our Native Americans and steal their wealth. Now we let them build casinos even though we usually prohibit ourselves from building them, and we gamble away our money to them. These are different things. This indicates a change in our behavior.

For your second paragraph, can you provide a source for that?