I want to know the answer to the following question:
For what  did Canadian natives use asphalt as a waterproofing material?
All the background I'm provided with is that "However, it wasn't until 1787 that fur trader and explorer Alexander MacKenzie saw the Athabasca oil sands and said, "At about 24 miles from the fork (of the Athabasca and Clearwater Rivers) are some bituminous fountains into which a pole of 20 feet long may be inserted without the least resistance."". Is that enough to answer the question?