1. What is a successful society? You may have a different definition but imho it’s one that hasn’t torn itself apart or causing active harm to itself.
2. I never said they didn’t have a concept of marriage, just that it’s not integral.
Both those points however are dramatically affected by colonization. Particularly Christian colonization, but not restricted to it.
Colonization both destroyed many otherwise successful societies and forced their own concepts onto the ones that remained.
As such I don’t think there’s any society that does have absolutely no concept of marriage, but there are some where marriage is not integral.
Various indigenous groups did not have a formal marriage, but did sometimes have a vow. Even within the US, you’d have the ancient traditions of hand fasting among settlers, which wasn’t a marriage but an informal vow.
The Mosuo/Na people of China famously do not marry.
Hence why I disambiguate between marriage and monogamous binding. heck, monogamous bindings for life are present in a lot of non human social norms too.
But marriage is different in that it’s a formalized procedure to do the binding, and in many cultures was tied to the religious or governmental authority figure as a form of bookkeeping and control, or to show political bindings.
And back to the point of causation/correlation, is marriage integral to success? I’d argue not since hand fasting continued into very relatively (to human history) recent times.