Upvote:10
Perhaps it depends on your precise definition of leather.
Since way back in Palaeolithic times, hunters had made used of the skins of the animals they killed for clothing and for shelters. They had learned to scrape off the inner layer with fat attached, and the outer layer with hair attached. To prevent the skin from decaying it could be sun-dried to give rawhide, or cured either with smoke or by rubbing with fats or oils. At this point it could be called leather, and according to its origin and treatment it could vary from hard and stiff to soft and supple. It was used for clothes, footwear, gloves, tents, buckets and many other things β even sails could be made of leather. It was a stronger alternative to cloth.
I suspect that this was as far as the Native Americans got. Europeans however were accustomed to using chemicals.
At some point it was discovered that soaking the skin in alum would give a soft, white leather, although it was not water-resistant. The major breakthrough came some time around the 5th century BC in the Roman Empire, when the tanning of leather was discovered. This involves soaking the leather in a solution of tannin, obtained from tree bark. It is an industrial process, requiring many different tubs of various strengths of tannin solution. The leather is gradually moved from one tub to another, successively increasing the solution strength, for a period of over a year. The tubs were usually placed well away from the town, as the smell was objectionable. The tannins combined permanently with the collagen in the skin to produce a leather that was waterproof, chemically stable and which would not decay. It was superior in quality to cured leather, although cured leather continued to be produced as it was easier to do. Sometimes a shoe would be made with a sole of tanned leather but an upper of cured leather.
The reference for the above is an article "Tanning and Leather" by Carol van Driel-Murray, in the book The Oxford Handbook of Engineering and Technology in the Classical World
As an aside, the leather tanneries using these traditional methods are one of the tourist sights of Fez in Morocco. You can see the skins moving from one vat to another with a stronger solution.