I always thought the northerly need for survival was the real origin of Christmas (Yuletide) gift-giving, actually. People too proud to take charity just might come up with a holiday at the winter solstice that involves trading gifts that you know certain neighbours need to get them by through the winter, because you know everyone in town, are related to most of 'em, and actually give a shit about them surviving to the spring. Isn't that what the decorated trees were for? Leaving anonymous gifts under? Usually I just remember seeing the "gifts of the magi to jesus" getting the credit, BUT if that were the case, we'd just be sacrificing incense and money. Oh, and it would explain the origin of making the gifts more or less anonymous (crediting them to "santa", as it later evolved into.)