I tried for several hours to find out about those research projects without any luck.
I think you should challenge your assumptions about “primitive” societies. Some Indigenous Australians in remote areas (where colonisers have not yet destroyed the ecosystems) continue to live in the same way they have for thousands of generations. They have very complex systems of lore and kinship ties, inspiring traditions of art, music, dance and story-telling and a deep relationship with the history of the land through ‘songlines’.
Controlled fires are used to return nutrients to the soil and to prevent larger ones happening. They did change their environment but in ways that were beneficial to all species. They are the world’s most ancient continuous culture, living on the driest continent on Earth, with uniquely nutrient-poor soil.
In my view they are not ‘weak’, but experts in sustainable living and we have much to learn from them.