Human nature is NOT socialism much less capitalism.
Probably one of the most ridiculous arguments I've seen is when leftists say that "socialism is human nature." Or, conversely, when libertarians say that "capitalism is human nature."
Capitalism and socialism are industrial systems. They're systems designed for the organization of an industrial society. Industrial society has existed for about 250 years, maybe 300-400 if you're using a very broad definition of industrialism. Humans have been around for at least 100,000 years, maybe longer.
Why on earth would we ever expect systems like capitalism or socialism - which are themselves responses to an incredibly new set of conditions - to embody human nature?