People with an aa genotype will express a recessive trait
World maps do have changed during the centuries because we grew in knowledge and technology, but the maps have also been shaped by differences in culture, religion, experience, and geography and also because of different natural disaster
The biggest doubling time of all the regions/continents in the world has Europe.
Europe is the only continent that has almost 0% population growth (as of 2014), which practically means that with this pace Europe will need an eternity to be able to double its population, so it makes it the continent with the biggest time needed to double it's population.
The air masses that have the greatest influence on weather conditions in the Midwestern United States are continental polar.
This air masses come from the north, they are heavy, low, cold and predominantly dry air masses, and are most intense in the colder part of the year. But they are not the only one, even though they are the dominant ones, the tropical warm and wet climate also has a big influence, especially in the warmer part of the year, and it's influence is gradually increasing.
May you show the map ? In the United States iron ore, metal, steel,.... maybe that helps
