A historian reviews several of his colleagues' books about early African states. He then writes his own book
summarizing the findings in these works and offering his
own opinions on their significance.

the answer would more than likely a.)falling crop prices  

hope the answer is right and ,either way have a nice day.

both eastern and western early north american cultures were known for building wigwams and longhouses.

wigwams, also called wetus, were small houses of 8-10 feet tall, made of wooden frames covered with woven mats and sheets that were used by algonquian indians. similarly,   longhouses were also used by algonquian and the iroquois tribes, and they were built as well with pole frames and elm bark covering. however, the main difference between wigwams and longhouses is that the latter was much larger than the former, with 200 feet long, 20 feet wide, and 20 feet high with inner raised platforms used for sleeping space.