This is an excellent point. The scaling of social accountability is a difficult problem. In my opinion it is a root problem of humanity and our current solutions are due for disruption.

It depends how groups are defined. Agriculture is a precondition for a society divided into classes (for social, not practical reasons). Groups from the beginning of human behavioral modernity to the rise of agricultural slave empires in Sumeria etc. 10,000 years back worked this way.

So from the drawing of cave paintings in El Castillo onward through the next 30,000 years, all humans lived like this. You could say it is human nature. Then class-divided society spread - 2000 years ago the modern Stockholm area was a classed society, whereas 200km north were hunter-gather bands. By modern day, hunter-gatherer areas have dwindled to remote areas.

The urge to have large numbers of people all under one grouping seems to be the impetus of a ruling class or ruler, from Alexander the Great to modern times. There are signs of hunter-gatherer bands in relations of mutual aid with other bands, for marriage and other things. One of the earliest pieces of literature, instructions of shuruppak, instructs rulers to get new slaves from far away lands.

(To reiterate a point from before - there is no evidence of class societies before 10,000 years ago. It is possible some tried to be a non-working ruling class, but the methods of production of migratory hunter gather bands made this difficult, and over a span of time impossible. Whereas with the rise of agriculture 10000 years ago, we have a mass of evidence of class societies.)

> Agriculture is a precondition for a society divided into classes (for social, not practical reasons).

I would completely reverse this... a society divided into classes is a precondition for agricultural society (for practical, not social reasons).

In the period of early civilization, convincing people to work 16 hours in the fields or in the mines is very difficult if they have any other viable option, including migrant hunter/gathering. Therefore, it is necessary to create a class of people that have no other viable options, either by slavery or other forms of inequality. The social structures surrounding inequality evolved as a method of maintaining this practical class stratification.

Indigenous Americans, prior to colonists’ arrival.

[source] Disney

Indigenous Americans practiced warfare, rape, slavery, and cannibalism no different than other peoples around the world.

This might had been the case in only low density areas (same as in all other continents), the majority of indigenous Americans did not live in classless societies.

Nobody said no classes. There wasn’t money like there was in Europe. There were by some intellectually honest estimates 50m people living in N and S America at the time of arrival, a huge number of people were living day to day without money.

I don't know of any, but does it need to?

Yes, unless you'd like our current society, which is astronomically larger than dunbar's number, to collapse, in a most likely very violent manner.