Final answer:
While it is difficult to determine the exact percentage, since all human societies began as band-level societies, it can be posited that everyone today has ancestors who once lived within such social structures. However, the complex history of human societal development makes it impossible to assign an accurate percentage.
Step-by-step explanation:
Assessing what percent of people living today had ancestors who lived in band-level political systems involves understanding both ancient and prehistoric societal structures. The archaeological consensus is that all societies started at the band level, which suggests that technically everyone today descends from such groups. However, such a precise percentage is not easily quantifiable due to multiple ancestral lines and the complexity of human migration and societal evolution.
Early human societies were primarily organized as band societies, small groups of typically 20 to 30 people that functioned without formal political structures. Decision-making was typically carried out through discussion and consensus, and individuals with knowledge or experience may have influenced decisions in specific areas. These band societies were prevalent until around 10,000-12,000 years ago before transitioning into complex forms such as tribes, chiefdoms, and eventually states and empires.
Given that modern nation-states, which are typically marked by centralized governments and bureaucratic institutions, have only existed for a small fraction of human history, it is reasonable to conclude that a significant portion of the population today had ancestors in band societies. However, every person's ancestry will include various types of political systems as it stretches back through time.