Linguistic Evolution

After watching the short yet increasingly thorough video, I was shocked at how much information a linguistic can acquire by comparing features and regular patterns between languages. 
Not only can they determine linguistic relationships, but they're also able to trace specific steps in their evolution and apply the reconstruction of earlier languages WITHOUT any kind of written record. Isn't that amazing? The video also pointed out that groups of people that shared a single language split up in multiple tribes, resulting in radically different languages. 
This specific part made me think of my own experiences, exclusively when I had first moved from Cairo to New York City. Because I had migrated and settled in a new place, every linguistic aspect of my daily life was different, even though I was still speaking the same language.
It just goes to show you what a critical role culture holds over a language and its evolution. As cultures increasingly grow, languages will continuously divide and separate into their own terms.