Humans started-out as 'simple' hunter gatherers - with no storage of
food and extremely little technology; and there are two distinguishable
paths by which hunter gatherers apparently began to evolve cultural
complexity - and increase their power.
These are exemplified by Eskimos which increased technology, and Australian Aborigines which increased cooperation.
If it is assumed that the lives of peoples like the the Kalahari Bushmen and similar adjacent groups like the Hazda represent something like the baseline state for human hunter gatherers - it can be seen that Australian Aborigines have a larger scale society, able to get larger numbers to cooperate.
Technologically they have even less than the Bushmen (e.g. lacked bows and arrows), but in a war the Aborigines would be able to field a considerably larger number of men.
The factor seem to be religion.As contrasted with the simple, rather undefined and very variable and fluid animism of the Bushmen; Aborigines have a complex totemic religion, and great effort is expended in preserving this unchanged between generations. It is likely that is is the sharing of a common religion (which is also linked with landscape knowledge, hence survival in arid desert conditions) is the key factor in enabling cooperation. But this seems to have happened without any significant increase in general intelligence.
The Eskimos, by contrast, remain a small scale society with small scale cooperation and ill-suited to warfare; but use several examples of advanced technology such as canoes and hunting weapons.
This technology is necessary for their survival in Arctic conditions; and technology seems to have been made possible by the evolution of higher intelligence. Eskimos may have the highest average intelligence of hunter gatherers, and a significantly higher level than either Bushmen or Aborigines.
Alone, neither larger scale cooperation nor advances in technology were enough make a complex society - together they form something like the basis of a complex, large scale, internally-specialized society such as the Pacific Northwest Amerindians (totem religion and technology).
And the implication is that high intelligence is necessary to preserve technological aspects, and cooperation (via religion) is necessary to preserve large scale cooperation.