I don't know if this is more of an askscience or askhistorians question so I am posting this in both subreddits. What I'm trying to ask is why extreme cold weather has not been more of a detriment to human survival. Northern Europe, USA, China all have nasty winters that are costly and often fatal. But not only have the northern halves of these areas flourished but they have maintained and continue to maintain a higher population density than their southern halves. I realize this isn't a hard set rule but why do people chose to live in places with these difficulties at all? There seems to be a lot of negatives and no positives.
Actually, population is most dense near the the tropic of cancer. There have been plenty of relatively population dense civilizations nearer to the equator, e.g. South China and Mesoamerica.
Contemporary cultures tend to be more economic developed outside of the tropics, such as the USA, Europe. However, these countries are not relatively very population dense compared to the rest of the world. This economic difference might be partially because the tropics tend to have a higher disease burden, e.g. malaria. The developmental economist Jeffery Sachs has written on this, though it's not universally accepted.
Tropical disease and climate prevented it. Tropical rainforests can't be farmed in general, because the continuous precipitation leaches all nutrients from the soil. Another problem were diseases like malaria and the sleeping sickness, which forced people to build cities in the mountains instead of lowlands. Tse-tse prevented the settlement of many lowlands in central Africa until the 20th century.
So as a result, tropical areas with wet and dry climate are now pretty densely settled. Areas with tropical rainforest climate - which are concentrated around the equator - are sparsely settled.
You may be interested in the 'Why did humans move to inhospitable regions?' section of the Popular Questions pages, as found in the sidebar.
