What did it look like in it's inception?
How has the understanding and practice of it changed throughout the centuries?
What major theological ideas surrounding it have come and gone? What has remained consistent?
What did most Christian theologians think about communion 200, 500, 1000, and 1500 years ago?
The folks over at /r/Catholicism would know lots about this topic (granted, they are biased, but who isn't?)