Jared Diamond made good use of maps that trace the spread and evolution of language, to connect groups of people across time and geography. Tying together subsets of Indo-European shows the clear relationships of groups that might be separated physically, but clearly have had contact and shared ideas.

And when I consider the disparate groups tied together by the common IndoEuropean heritage, it's pretty amazing: India to Britain all speak languages that descend from a common root. I have a theory that when the English made it to India, they found a people at once exotic yet strangely familiar; the unfortunate term "White Oriental Gentlemen" embodies a peculiarly English compliment, as if to say "these people don't look like us, but damn, there's something familiar about them". Looking at the map of the spread of people and language out of the Fertile Crescent, I see India and Britain at opposite ends, but at about the same distance, of the spread of culture to the east and west. Maybe it's something like birth order--their cultures traveled a similar "distance" in space and time and perhaps experienced similar influences. (Or I could be entirely full of it, but this is why I've been looking for histories of India.)

Alphabets reveal information beyond the record of language. The change from hieratic symbol systems with a one-to-one mapping with a real thing or action, to "compositional" systems made up of smaller units of letters/sounds/syllables (I'm making up my terms as I go, sorry), represents a fundamental shift in the way people thought, away from strict literalism to an ability to think new thoughts composed of pieces of other thoughts, and abstractions that didn't have to be represented by an existing thing/action. I'd call it "empowering", in that hieratic systems are passive in their dependence on an existing reality, while alphabets/compositional systems are active in the way that they give people the power to create new words representing new concepts.

It shows the power of literacy and an alphabet. People who possessed both routinely steamrollered people with less literacy and hieratic writing systems. They could think bigger thoughts.