In our 
rise to today’s modern, civilized world, which advance was the most important? Many think it was the use of tools, the discovery of controlled fire, or development of language. But a new book by neuroanthropologist John S. Allen argues our move out of the elements and into dwellings may have been the key. When we discovered housing, we could protect ourselves from the weather and predators, and begin to organize in families. A secure living space enabled us to sleep soundly, which (as you might have discovered for yourself), is very important for brain functions. Allen thinks homes are “critical not only for resting but also for thinking.”
Could this be the underlying reason for homesickness?
I have not read this myself, but it caught my eye when I saw a brief review in the Jan. 18, 2016 issue of Time magazine (page 26). The title is Home: How Habitat Made Us Human.