My scholarship on this is anything but perfect (or scholarly, for that matter). If I confine myself to internet sources and my own blog entries, it's for convenience sake and a nod to the forum where these ideas are presented; it's not a very strong defense of said ideas.
Still, there is a lot of annual nonsense about Christmas "traditions" being stolen from "pagans." And the silliest part about such claims is how ahistorical they are, all the while asserting a knowledge of history superior to those of us fooled by the "pagan" practices we perpetuate in the name of something holy.
So let's lay it out in careful fashion. First: Christmas was not observed by the Church (the "Roman" church, but at the time, the only church) until the 4th century C.E. There was an observance of the birth day of the Christ in Egypt in the 3rd century, not surprising as the Egyptians observed the birthdays of their Pharoahs, whom they considered gods at birth (and so their birthdays were significant).* But Rome didn't pick up the practice until sometime in the mid 4th century. To put that in historical context as far as "pagan" practices go:
In the late 4th century, persecution of pagans by newly Christian Romans had reached new levels of intensity. Temples and statues were destroyed throughout the Roman empire: pagan rituals became forbidden under punishment of death, and libraries were closed. In 391, Emperor Theodosius I ordered the destruction of all pagan temples, and the Patriarch Theophilus complied with his request. One theory has it that the great Library of Alexandria and the Serapeum were destroyed about this time.Not, in other words, a lot of interest in taking up "pagan" (I used the word advisedly) practices at the time. Certainly there were no Christmas trees in 4th century Rome, no holly and ivy, no boar's heads or even Santa Claus.
Then comes the medieval period, and Christmas feasts, which if "Sir Gawain and the Green Knight" is any evidence, were the common feature of Christmas celebrations (again, no holly and ivy, no Christmas tree, no jolly old St. Nick; just the boar's head and lots of hunting). But I jump to medieval Europe because that's when the passion plays began, and in Germany (influenced by the "East," which is to say the Orthodox church, which observes the festal day of Adam and Eve), a feature of some of these plays became the Paradeisbaum, the tree of Paradise, because of the feast of Adam and Eve.
CHRISTMAS Eve is the feast day of our first parents, Adam and Eve. They are commemorated as saints in the calendars of the Eastern churches (Greeks, Syrians, Copts). Under the influence of this Oriental practice, their veneration spread also to the West and became very popular toward the end of the first millennium of the Christian era. The Latin church has never officially introduced their feast, though it did not prohibit their popular veneration. In many old churches of Europe their statues may still be seen among the images of the saints. Boys and girls who bore the names of Adam and Eve (quite popular in past centuries) celebrated their "Name Day" with great rejoicing. In Germany the custom began in the sixteenth century of putting up a "paradise tree" in the homes to honor the first parents. This was a fir tree laden with apples, and from it developed the modern Christmas tree.So the "Christmas Tree" began, not with tree-worshiping Druids in England (why would you cut down and kill what you worship? That's a very modern idea, not a very ancient one.), but with Christian Germans in the 16th century. It finally became a feature of Christmas observances in the home in the 19th century. You don't see them in most churches (especially the older mainline churches), at least not in the worship space, and they have nothing to do with Christianity (in fact some try to blunt their secular connections with a nativity scene; I know my family did when I was a child.). And what about gift giving? For that, you can blame Clement Clark Moore.
The popular assertion is that gift giving at Christmas is connected to the Roman Saturnalia. The problem is, that practice died out in Rome before the 4th century; and gift giving didn't become a part of Christmas until the 19th century. The closest you get to that in Europe is the sharing of food with the peasants by the landowners, but that practice is more related to the Feast of Fools that allowed the repressed a brief respite from their oppression (probably enough to keep them happy in their servitude) and the quite reasonable function of not letting the serfs starve in the winter (again, just enough to keep them in their place). The exchange of gifts between Gawain and the Green Knight is more typical. They aren't gifts in our modern sense at all, and they are exchanged between peers, are in fact part of a game.** Even today our gift giving is between peers (our friends and co-workers) or within family (especially to children, where we recapitulate the relationship of lord and serf), and only occasionally to the "poor" (whom we never go to Black Friday sales for).
If you follow all the links in this post, several will send you to my archives where you will find collected posts in categories that overlap several of them; so there's a lot of repetition and some tedious data-mining if you want to get down to the bedrock; which is, in places, still rather spongy. Suffice it to say that Christmas is pretty much a modern invention, especially as we observe it in America. I rather like the conclusion one of my posts drew, based on the work of real scholars and historians, that Christmas was one of the first holidays America had (thanks to the Puritans and the lack of a single Church, as well as a mixture of European cultures, we had no holidays of our own that all could observe from the beginning); it was open both to the religious and the secular. You could observe the birth of Christ, or just observe a modern version of the Feast of Fools. But it was all about celebrating and enjoying your family and friends, and that's still what it should be.
*Origen, glancing perhaps at the discreditable imperial Natalitia, asserts (in Lev. Hom. viii in Migne, P.G., XII, 495) that in the Scriptures sinners alone, not saints, celebrate their birthday; Arnobius (VII, 32 in P.L., V, 1264) can still ridicule the "birthdays" of the gods. New Advent.
** Games were associated with Christmas celebrations down through Dicken's A Christmas Carol where Scrooge's nephew and friends play them on Christmas Day. Sadly that is no longer an expected feature of our Christmas revels.