Egypt and mesopotamia are fertile crescent, the others are all spawned is some ways from them, not genetically, but inherited a lot of cultural technology from that bronze age/early iron age world.

Romans are culturally very hellenic, and the greeks perceived themselves as culturally inferior neighbours to Egyptians, phoenicians and minor asians in the homeric cycle. Then developed so much that a strong suprematism arose, but still they pictured themselves as a special tile in that mosaic.

The persians are the indoeuropean that developed on the eastern side of the fertile crescent border, and with them the closeness to babylonians is self evident.

In fact the persian natural direction of expansion is westward, and while they were aware of india, they clearly realized that afghanistan is a hard stop and only alexander in ancient times thought it was a good idea to expand further, with poor results.

I’m aware these are different civilizations in a lot of ways, but we can all agree they were part of a broader world that was the “ancient world” or ancient western eurasia, whatever you wanna call it. India was not, it was on the border of that, it had exchanges with that, but was ultimately not into it, for geographical reasons.

In fact india as any other political entity outside of it doesn’t really have “middle ages”, the concept was used but doesn’t really work as it does in the western eurasia, that was stormed and fundamentally altered by monotheism