I want to know the answer to the following question:
Simpson laid the systematics of mammal origins and was taught universally up until the end of what century?
All the background I'm provided with is that "Since Simpson's classification, the paleontological record has been recalibrated, and the intervening years have seen much debate and progress concerning the theoretical underpinnings of systematization itself, partly through the new concept of cladistics.". Is that enough to answer the question?