If we are all descendants of Noah’s sons, how is it there are many cultures where the disparity of knowledge is so vast? How would it be possible to “forget’ the basics of a culture one came from when it would have been every day practicality? How would people change so much, and in such a short time?
It only takes one generation to change a culture. For example, after God had done His miraculous work bringing the Israelites out of Egypt and into the promised land, Judges 2:10 tells us that the next generation neither knew the Lord nor what He had done for Israel.
According to Genesis 10:5, 20, and 31 each of the 70 family groups that came from Noah’s three sons had their own language. That means there were 70 independent cultures adopting new ways all at once with out any coordination between them. I think you can see how they could become noticeably different within just a few generations. There have been nearly 100 generations since then.