Re Noah. There is archaeological evidence that there was a Great Flood in the Middle East a few millenia ago. To our biblical historians their part of the world was
The World, therefore
The World was destroyed by flood.
Noah, having some prescience of impending weather conditions, builds his ark.
The World (the Middle East) doesn't contain elephants, giraffes and such but it does contain sheep, goats, camels, fowls etc. so he takes a breeding pair of each on board, with an eye to the future. Along with them there's going to be all the insects - try keeping ticks etc. off sheep.
When the water subsides there's Noah, his wife and family (sons are mentioned in the bible, they probably had wives and children) and the stock - repopulation of
The World. Meanwhile, in the rest of the world that isn't
The World, things probably carry on pretty much as usual.
