Famine- High population means more mouths to feed
Disease- Diseases usually spread more quickly with people who live closer( as it can just move from one person to the other)
War- People like to fight for land, resources, money, etc. And having more of those things mean they are more able to support families, communities, and more.
(Hope this helps a little)
This is true a theory is an explanation of observable facts and phenomena.
In the southern hemisphere, the tundra includes Antarctica. The arctic tundra in the northern hemisphere includes parts of Russia, Iceland, Canada, Norway, Greenland, and Alaska (state in the US).
