Brahmin are in the highest caste of Indian society, it is a cast reserved for holy men. Dalit, Shudra, Kshatriyas and Vaishya represent the untouchables, laborers, nobles and artisans respectively. The caste system is rigid and there is very little crossover between classes.

Difficulty in collecting taxes was a major contributing factor to the fall of both the Han and Roman empires. In the Roman Empire, wealthy land owners avoided paying taxes, and tax collectors were often driven away by the private armies of these wealthy landowners. In the Han Empire, scholar officials were not required to pay taxes, and an increase in population led to smaller family farm operations, which in turn made it more difficult for people—especially in the peasant class—to pay taxes.

While the population increase in the Han Empire contributed to its collapse, the collapse of the Roman Empire was partially attributable to population decreases caused by plagues.

Invasion by the Huns and the Visigoths took place only in the Roman Empire, not in the Han Empire.

The caste system is a system of social hierarchy that is most commonly associated with India and Indian history.

Tiberius and Gaius Gracchus were two Romans of noble heritage who attempted to pass land reform legislation and other measures to even the wealth disparity in Rome. Obviously, both were very unpopular with patrician classes, especially as their demonstrations had the habit of turning into angry mobs. While each brother was murdered (first Tiberius, then Gaius years later), their ideas and roles as champions of the common man live on. 

The primary cause of tensions between Romans and Jews during the Jewish occupation of Israel, was the refusal of the Jewish people to accept the Roman Emperor as a living deity. At the time of Roman occupation, the emperor was considered divine and all conquered peoples were expected to recognize his divinity. The monotheistic Jewish people believed this violated one of their most sacred rules, and so, refused.

The Roman society, at its heart, was divided into those with noble ancestry (Patricians) and those without it (Plebeians). Patricians tended to be the ruling class, construing most of the senate and other important positions of state. Plebeians were everyone else. However, there was definitely grey area; plebeian families looking for more legitimacy could marry into older, poorer, patrician families. Also, if a plebeian family was notable enough and rich enough for long enough, they would eventually become patricians (at least in practice).  

Helots were serfs in ancient Spartan society. They did the majority of the hard labor in ancient Sparta and, like all serfs, were bound to the land they worked on. They also greatly outnumbered the rest of the population of Sparta. They were, however, not known for their fighting prowess and were not trained in combat like a regular citizen of Sparta might be.

Patricians, in the Roman Republic (particularly the early years), were aristocrats who had significant legislative authority. They were distinct from plebeians and from less noble families in the Republic.

Helots were serfs/slaves in ancient Spartan society. Helots were owned by the state and were bound to the land. They enjoyed some privileges that slaves did not, but practically speaking they were serfs who were tied to the land. Most Helots were comprised of the defeated enemies of Sparta.

As the Mauryan empire is in India, the caste system, which serves as the foundation of Hinduism (founded in India), would be the social feature found there. The dominance of bureaucratic and landholding elites would be found in China, where a bureaucracy based off Confucian civil service examinations had been established. Persia, more than likely, had a benevolent posture toward minorities, as minorities were seen as low in the caste system. Finally, Rome and Greece saw the role of slavery as unusually high compared to other empires of this era.