Please show where the apostles taught the assumption of Mary. Or is that an example of "not been true to the original teachings of the Apostles"?
The Assumption of Mary is not in the Scriptures. Neither is it ruled out in the Scriptures. (After all, far lesser than she were taken bodily up to heaven. The Assumption of Elijah comes to mind.) It is in the spelled-with-a-capital-letter, big-T Tradition.
Nobody ever found, nor claimed to ind, nor so much as credited the possibility of finding, bodily remains of Mary. Not even relic-hunter Empress Helena, for whom such a coup would have been a matchless feather in her imperial cap. Not even all the Israeli Antiquities Authority people or their equivalent back in the day. Even during the centuries when people were quite gaga about relics. As the Pope Pius XII (1950) reasoned, “Finally, since the Church has never sought for bodily relics of the Blessed Virgin, nor exposed them for the veneration of the faithful, we have an argument which can be considered as 'practically a proof by sensory experience'" (AAS 42. 765-66).
The bottom line: although the Papal declaration of the Assumption as a dogma (Munificentissimus Deus) was not published until 1950, it had been first believed by the ancient Christian community (sensus fidelium), then celebrated liturgically, then supported by scholastic argument from Scripture, and lastly --- many centuries later--- formally defined as a dogma of the Faith.
That, by the way, is the normal course of doctrine: it is first anciently believed; then celebrated; then clarified by argument, then defined. And not the other way around.
This article supplies a more cohesive explaanation. Scroll half way down Assumption -- Page 7 (LINK) or here's the PDF version: ASSUMPTION -- Page 7 - 9 (LINK)--- It'll take you some time to digest, but if you really want to understand this bit o'popery --- perhaps for the purpose of blasting it more accurately, eh? --- there it is.
Enjoy, Brother Bear!