Nobody knows what kinds of habits and belief systems existed earlier than in known historical records (which were mostly written or artistically supervised by sporadic patricians).
That, to me, is the most important point made so far.
That's what I'm alluding to when I say that I care only about what Christmas (or Easter, or Fourth Of July, for that matter) means today. The rest is a fun history exercise, but that's about it. It's nice to know where putting up a Christmas tree came from, but if it were suddenly discovered that humans a thousand years ago viewed trees as evil spirits and each family felt the need to murder one symbolically as a message to all the other trees to keep well behaved, would it change what I do today, in 2020? Hell no! I'm all about that tree!
I was raised in a pretty severe fundamentalist home. We weren't allowed to go trick-or-treating (poor me, huh?) because it was "satanism" and a way to lure children into the service of the devil. To me, after talking to kids at school the next day, it really just seemed like a day to haul in a buttload of candy and dress up...two of my favorite things. I really would love to see Ol' Scratch pop up and see what we've done to his holiday:
*POOF*
"So, my minions, have you kept Halloween pure and true to my message of evil and hate?! Have you spread discord and wickedness among yourselves?!"
"Ahhhh, well, we started to, maybe, but that was a lot of work. Now we mainly just dress the kids up like princesses, cowboys, that sort of thing, and send them round the houses for candy."
Sorry, we've bunged it up for you, haha!
And somebody help those poor dogs, they're getting it handed to them!