The trick is not have "wealth" (ie property ownership/rights). Societies that were nomadic with low/no property ownership culture did not have wealth inequality since there wasn't that much "wealth" to have. They had their hierarchies but those were weak, more akin to the kind of hierarchies you have in families ("everyone listens to grandma" kind of hierarchy). Wealth inequality is obviously synthetic (and this study is kind of silly), since you need a governing body to maintain property rights (along with creating what today are the most valuable legal ownership structures, like intellectual property). A corporation, a mortgage, a deed, equity, all the defining elements of wealth, are exclusively legal constructs created/administered by governments. The wealth of every wealthy person you can think of is based on their rights to property, not the property itself (i.e stocks, deeds, trademarks, copyrights etc.). This requires a very elaborate infrastructure to maintain and a culture to support it. Wealth isn't a given and actually is very easily destroyed (when governments are toppled or property rights are taken away--Communist rebellions of the twentieth century are a good example).
It's true that formal wealth systems (like land, stock ownership and trademarks) require an elaborate legal and cultural infrastructure to maintain — but only at scale. The absence of such systems doesn't eliminate wealth inequality, it just changes how it's enforced.
In less formal or collapsed systems, wealth and resources are often controlled by a ruling oligarchy or individuals whose hard power acts as a de facto property right.
For example, many argue that Vladimir Putin is one of the wealthiest individuals in the world, despite lacking formal ownership on paper — his political and military power effectively grants him control over immense resources. Wealth inequality ultimately stems from control over resources, whether legitimized by law or enforced through power.
Power people have power because of power is more of a movie trope than the actual mechanics of the world you live in. Wealth is exclusively abstract legal constructs in the modern world. You might be surprised to know that even Putin's wealth is tied to legal ownership structures, (regardless if they're maintained by bogus shell companies, he has effective rights to the property). Whatever niche counter-example comes after doesn't influence how global inequality is administered or experienced by the majority of people.
