>>European colonial powers were simply the first to outsource this dynamic into other continents. While most people in Europe did not directly benefit from native or African slaves in the Americas the transfer of wealth allowed them to import grain and other products from abroad which simultaneously freed up enough labor to develop mining and other industries and increased the purchasing power enough to create significant demand for manufactured goods.

Is there any evidence to support this? I remember reading that exploitive practices like slavery added very little to Europe's GDP. There seems to be processes - like advancing textile production and coal mining technology and metallurgy - that began long before the age of colonialism, and thus would likely have continued even in the absence of the slave trade.