Immortality, but people in primitive society

During the day, Bai Tian transmigrated to the late matriarchal primitive society, a place teeming with ferocious beasts and where everyone possessed superhuman strength. Fortunately, Bai Tian possessed immortality, and as long as he didn't do anything reckless, he could eventually survive until modern society. However, even in a primitive society, one can unexpectedly become a father! Okay, to prevent his children from going hungry, he decided to stop lying around. He built houses, smelted iron, created writing… But, instead of developing into a modern society, why did it turn into a world of cultivation?!