One similarity was that religious leaders were also political leaders (to various degrees) in both entities. This meant that their power would not be as challenged by the citizens (after all, their leaders were god-sent, and opposing them could lead to God's wrath). Also, in this way, the entities could control their subjects better, because they controlled their private life too (including private ceremonies, such as marriages). <span />
Sometimes people engage in trade in order to get what they need or to communicate.
There are several ways in which we could justify this statement, but also many ways in which we would be able to challenge it.
In terms of support, we can argue that this was the case because the cultures of America did not have any significant contact with the cultures of Africa or Oceania until the arrival of the Europeans. We can also support this by the fact that the Andean cultures and the Mesoamerican cultures had no contact with each other.
However, there are several factors that show that this was not the case, or that the claim might be exaggerated. For example, we know that many groups in Africa had extensive interactions with each other. For example, the expansion of the Bantu that took place over large regions in Africa. Another challenge could be the extensive contact that many Mesoamerican groups had with each other.
The result of the noise will be a diminished recency effect but no impact on how well the other words in the list are recalled. The recency effect is the occurrence that when people are questioned to remembrance in any sequence the items on a list, those that come at the end of the list are more probable to be remembered than the others.
