Final answer:
Herodotus noticed a diverse range of societal customs, indicating an early form of cultural relativism. He documented these differences in his 'Histories', recognizing complexities and strengths in other cultures despite his own society's tendency to label them as 'barbarians'. His objective documentation style and awareness of cultural relativism have significantly influenced the field of history.
Step-by-step explanation:
What Herodotus noticed about people and their customs was the diverse and often conflicting nature of societal practices and beliefs. Herodotus's inquisitions into these aspects of different cultures showcased an early form of cultural relativism, as he questioned whether one culture could be deemed 'better' than another. This was especially significant given his Greek background, where other societies were often labeled as 'barbarians', particularly the Persians during the Greco-Persian wars. In his observations, detailed in the 'Histories', he describes various Thracian customs which differed vastly from Greek traditions, indicating his awareness of the wide spectrum of human culture.
Herodotus's studies extended to multiple societies, from the Thracians to Persia, noting intricate societal customs such as the differing views on birth and death among the Thracians, the warrior culture that esteemed those who lived off war and robbery, and the various marital practices. These observations highlighted that although Greeks like Herodotus used the term 'barbarian' to describe non-Greeks, the historian recognized the complexity of foreign societies and their potential strengths in unity and resources.
His accounts serve as a crucial resource for understanding not only historical events but also the historical and cultural viewpoint of ancient Greek society comparing to those they encountered or fought against. Herodotus's willingness to travel, read multiple sources, and document foreign cultures, using what would be considered a primary source-based approach to history, laid the groundwork for modern historical study and offers invaluable insights into the ancient world.